scholarly journals Satellite Estimation and Ground Based Measurements of Solar UV Index in Kathmandu

2014 ◽  
Vol 9 (1) ◽  
pp. 18-26
Author(s):  
Niranjan Prasad Sharma
Keyword(s):  
Solar Radiation ◽  
Spectral Range ◽  
Ozone Monitoring Instrument ◽  
Monsoon Period ◽  
Uv Index ◽  
Uv Irradiance ◽  
Before And After ◽  
Solar Uv ◽  
Ozone Monitoring ◽  
Ozone Column

The study is based on the satellite estimation and ground measurements of solar UV index in Kathmandu for the year 2009. Kathmandu (27.720N, 85.320E) is located at an elevation of 1350m from the sea level. The ground based measurement and satellite estimation was performed by NILU-UV irradiance meter and EOS Aura OMI spacecraft. The NILU-UV irradiance meter measures UV radiation in different spectral range. The Ozone Monitoring Instrument (OMI) is a spectrometer designed to monitor solar radiation in spectral range of (270-500) nm. This study shows that satellite overestimates the ground based (GB) UV Index (UVI) before monsoon by 103.6 % whereas during the monsoon period overestimation comes down to 70.8 %. The correlation coefficient (r) between ozone column from satellite and ground based measurement before monsoon and after monsoon is also studied. It is observed that the correlation between satellite estimated ozone column and ground based ozone column before and after monsoon is 0.83. The study showed that the estimation of OMI before monsoon is high than after monsoon. DOI: http://dx.doi.org/10.3126/jie.v9i1.10664Journal of the Institute of Engineering, Vol. 9, No. 1, pp. 18–26

scholarly journals Solar UV Index at Different Altitudes of Nepal

2018 ◽  
Vol 14 (1) ◽  
pp. 200-205
Author(s):  
Niranjan Prasad Sharma
Keyword(s):  
Flat Surface ◽  
Scattered Light ◽  
Visible Spectrum ◽  
Ozone Monitoring Instrument ◽  
Uv Index ◽  
Uv Irradiance ◽  
Solar Uv ◽  
Ozone Monitoring ◽  
Solar Ultraviolet ◽  
Ultraviolet Index

The main objective of this research is to study the satellite estimated solar Ultraviolet data alongside the ground based data in Nepal. Kathmandu (27.72°N, 85.32°>E), Pokhara (28.22°N, 83.32°E) Biratnagar (26.45°N, 87.27°E) and Lukla (27.69°N, 86.73°E) are located at an elevation of 1350m, 800m, 72m and 2850m respectively from the sea level. The ground based measurements and the satellite estimation were performed by NILU-UV irradiance meter and EOS Aura OMI satellite respectively. The NILU-UV irradiance meter is a six channel radiometer designed to measure hemispherical irradiances on a flat surface. Meanwhile the Ozone Monitoring Instrument (OMI) on board, the NASA EOS Aura space craft is a nadir viewing spectrometer that measures solar reflected and back scattered light in ultraviolet and visible spectrum. The study was performed for 3 years Ultraviolet Radiation (UVR) data. This study showed that the ratio of predicted OMI Ultraviolet Index (UVI) to that determined from the ground based measurement was less than 1.21 except in Lukla.Journal of the Institute of Engineering, 2018, 14(1): 200-205

scholarly journals Comparison of Ground Based Measurements of Solar UV Index with Satellite Estimation at Four Sites of Nepal

1970 ◽  
Vol 8 (3) ◽  
pp. 58-71 ◽  
Author(s):  
Niranjan P Sharma ◽  
Binod K Bhattarai ◽  
Balkrishna Sapkota ◽  
Berit Kjeldstad
Keyword(s):  
Flat Surface ◽  
Scattered Light ◽  
Single Point ◽  
Visible Spectrum ◽  
Ozone Monitoring Instrument ◽  
Monsoon Period ◽  
Uv Index ◽  
Ground Measurement ◽  
Solar Uv ◽  
Ozone Column

The main objective of this study is to compare the ground based measurements and satellite estimation of solar UV index in four sites namely, Kathmandu, Pokhara, Biratnagar and Lukla. Kathmandu (27.72°N, 85.32°E), Pokhara (28.22°N, 83.32°E) Biratnagar (26.45°N, 87.27° E) and Lukla ( 27.69°N, 86.73°E) and are located at an elevation of 1350m, 800m, 72m and 2850m respectively from the sea level. The ground based measurements and satellite estimation were performed by NILUUV irradiance meter and EOS Aura OMI satellite. The NILUUV irradiance meter is a six channel radiometer designed to measure hemispherical irradiances on a flat surface. The Ozone Monitoring Instrument (OMI) on board, the NASA EOS Aura space craft is a nadir viewing spectrometer that measures solar reflected and back scattered light in ultraviolet and visible spectrum. The study shows that OMI overestimate the ground based data before monsoon by 71.28%, 47.29%, 27.92% and 35.83% respectively at Kathmandu, Pokhara, Biratnagar and Lukla. However during the monsoon period the same comes down to 8.55%, 15.63%, 10.74%, and 11.33% respectively. The main reason behind these discrepancies might be due to the spatial resolution of the satellite which estimates the UV Index on the basis of 13×24 km2 in nadir where as the ground measurement is for a single point. The correlation between satellite derived and ground measured ozone column was found to be 91 % and 89% for Kathmandu and Lukla respectively. DOI: http://dx.doi.org/10.3126/jie.v8i3.5932 JIE 2011; 8(3): 58-71

scholarly journals Measurements of UV irradiance within the area of one satellite pixel

2008 ◽  
Vol 8 (1) ◽  
pp. 3693-3720 ◽  
Author(s):  
P. Weihs ◽  
M. Blumthaler ◽  
H. E. Rieder ◽  
A. Kreuter ◽  
S. Simic ◽  
...  
Keyword(s):  
Reference Data ◽  
Ozone Monitoring Instrument ◽  
Uv Index ◽  
Clear Sky ◽  
Uv Irradiance ◽  
Ozone Monitoring ◽  
Time Periods ◽  
The Difference ◽  
Sky Conditions ◽  
Better Than

Abstract. A measurement campaign was performed in the region of Vienna and its surroundings from May to July 2007. Within the scope of this campaign erythemal UV was measured at six ground stations within a radius of 30 km. First, the homogeneity of the UV levels within the area of one satellite pixel was studied. Second, the ground UV was compared to ground UV retrieved by the ozone monitoring instrument (OMI) onboard the NASA EOS Aura Spacecraft. During clear sky conditions the difference in erythemal UV measured by the different stations was within the measurement uncertainty of 8%. For partly cloudy conditions and total overcast conditions the discrepancy of momentary values between the stations is up to 200% or even higher. If averages of the UV index over longer time periods are compared the difference between the stations decreases strongly. The agreement is better than 20% within a distance of 10 km between the stations for 3 h averages. The comparison with OMI UV showed for clear sky conditions higher satellite retrieved UV values by on the average approximately 15%. For partly cloudy and overcast conditions the OMI derived surface UV estimates show larger deviation from the ground-based reference data, and even bigger systematic positive bias.

scholarly journals Ozone Monitoring Instrument spectral UV irradiance products: comparison with ground based measurements at an urban environment

2008 ◽  
Vol 8 (5) ◽  
pp. 17467-17493 ◽  
Author(s):  
S. Kazadzis ◽  
A. Bais ◽  
A. Arola ◽  
N. Krotkov ◽  
N. Kouremeti ◽  
...  
Keyword(s):  
Global Scale ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Ozone Monitoring Instrument ◽  
Model Calculations ◽  
Aerosol Absorption ◽  
Theoretical Approaches ◽  
Uv Irradiance ◽  
Ozone Monitoring ◽  
Comparison Period

Abstract. We have compared spectral ultraviolet overpass irradiances from the Ozone Monitoring Instruments (OMI) against ground-based Brewer measurements at Thessaloniki, Greece from September 2004 to December 2007. It is demonstrated that OMI overestimates UV irradiances by 30%, 17% and 13% for 305 nm, 324 nm, and 380 nm respectively and 20% for erythemally weighted irradiance. The bias between OMI and Brewer increases with increasing aerosol absorption optical thickness. We present methodologies that can be applied for correcting this bias based on experimental results derived from the comparison period and also theoretical approaches using radiative transfer model calculations. All correction approaches minimize the bias and the standard deviation of the ratio OMI versus Brewer ratio. According to the results, the best correction approach suggests that the OMI UV product has to be multiplied by a correction factor CA(λ) are in the order of 0.8, 0.88 and 0.9 for 305 nm, 324 nm and 380 nm respectively. Limitations and possibilities for applying such methodologies in a global scale are also discussed.

scholarly journals Monitoring Solar Radiation UV Exposure in the Comoros

2021 ◽  
Vol 18 (19) ◽  
pp. 10475
Author(s):  
Kévin Lamy ◽  
Marion Ranaivombola ◽  
Hassan Bencherif ◽  
Thierry Portafaix ◽  
Mohamed Abdoulwahab Toihir ◽  
...  
Keyword(s):  
Ultraviolet Radiation ◽  
Cloud Cover ◽  
Relative Difference ◽  
Ozone Monitoring Instrument ◽  
Uv Index ◽  
Measurement Campaign ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
Sky Conditions ◽  
Very High

As part of the UV-Indien project, a station for measuring ultraviolet radiation and the cloud fraction was installed in December 2019 in Moroni, the capital of the Comoros, situated on the west coast of the island of Ngazidja. A ground measurement campaign was also carried out on 12 January 2020 during the ascent of Mount Karthala, located in the center of the island of Ngazidja. In addition, satellite estimates (Ozone Monitoring Instrument and TROPOspheric Monitoring Instrument) and model outputs (Copernicus Atmospheric Monitoring Service and Tropospheric Ultraviolet Model) were combined for this same region. On the one hand, these different measurements and estimates make it possible to quantify, evaluate, and monitor the health risk linked to exposure to ultraviolet radiation in this region and, on the other, they help to understand how cloud cover influences the variability of UV-radiation on the ground. The measurements of the Ozone Monitoring Instrument onboard the EOS-AURA satellite, being the longest timeseries of ultraviolet measurements available in this region, make it possible to quantify the meteorological conditions in Moroni and to show that more than 80% of the ultraviolet indices are classified as high, and that 60% of these are classified as extreme. The cloud cover measured in Moroni by an All Sky Camera was used to distinguish between the cases of UV index measurements taken under clear or cloudy sky conditions. The ground-based measurements thus made it possible to describe the variability of the diurnal cycle of the UV index and the influence of cloud cover on this parameter. They also permitted the satellite measurements and the results of the simulations to be validated. In clear sky conditions, a relative difference of between 6 and 11% was obtained between satellite or model estimates and ground measurements. The ultraviolet index measurement campaign on Mount Karthala showed maximum one-minute standard erythemal doses at 0.3 J·m−2 and very high daily cumulative erythemal doses, at more than 80 J·m−2. These very high levels are also observed throughout the year and all skin phototypes can exceed the daily erythemal dose threshold, at more than 20 J·m−2.

Variations of UV irradiance at Antarctic station Concordia during the springs of 2008 and 2009

2011 ◽  
Vol 23 (4) ◽  
pp. 389-398 ◽  
Author(s):  
Vito Vitale ◽  
Boyan Petkov ◽  
Florence Goutail ◽  
Christian Lanconelli ◽  
Angelo Lupi ◽  
...  
Keyword(s):  
Spectral Band ◽  
Field Measurements ◽  
Maximum Level ◽  
Ultraviolet B ◽  
Uv Irradiance ◽  
Solar Uv ◽  
Solar Uv Irradiance ◽  
Atmospheric Transmittance ◽  
The Impact ◽  
Ozone Column

AbstractThe features of solar UV irradiance measured at the Italian-French Antarctic Plateau station, Concordia, during the springs of 2008 and 2009 are presented and discussed. In order to study the impact of the large springtime variations in total ozone column on the fraction of ultraviolet B (UV-B) irradiance (fromc.290–315 nm) reaching the Earth surface, irradiance datasets corresponding to fixed solar zenith angles (SZAs = 65°, 75° and 85°) are correlated to the daily ozone column provided by different instruments. For these SZAs the radiation amplification factor varied from 1.58–1.94 at 306 nm and from 0.68–0.88 at 314 nm. The ultraviolet index reached a maximum level of 8 in the summer, corresponding to the typical average summer value for mid latitude sites. The solar irradiance pertaining to the ultraviolet A (UV-A, 315–400 nm) spectral band was found to depend closely on variations of atmospheric transmittance characteristics as reported by previous studies. Model simulations of UV-B irradiance showed a good agreement with field measurements at 65° and 75° SZAs. For SZA = 85° the ozone vertical distribution significantly impacted model estimations. Sensitivity analysis performed by hypothetically varying the ozone distribution revealed some features of the ozone profiles that occurred in the period studied here.

scholarly journals Quality assessment of solar UV irradiance measured with array spectroradiometers

2016 ◽  
Vol 9 (4) ◽  
pp. 1553-1567 ◽  
Author(s):  
Luca Egli ◽  
Julian Gröbner ◽  
Gregor Hülsen ◽  
Luciano Bachmann ◽  
Mario Blumthaler ◽  
...  
Keyword(s):  
Spectral Irradiance ◽  
Stray Light ◽  
Atmospheric Conditions ◽  
End User ◽  
Uv Index ◽  
Uv Irradiance ◽  
The World ◽  
Solar Uv ◽  
Solar Uv Irradiance

Abstract. The reliable quantification of ultraviolet (UV) radiation at the earth's surface requires accurate measurements of spectral global solar UV irradiance in order to determine the UV exposure to human skin and to understand long-term trends in this parameter. Array spectroradiometers (ASRMs) are small, light, robust and cost-effective instruments, and are increasingly used for spectral irradiance measurements. Within the European EMRP ENV03 project “Solar UV”, new devices, guidelines and characterization methods have been developed to improve solar UV measurements with ASRMs, and support to the end user community has been provided. In order to assess the quality of 14 end user ASRMs, a solar UV intercomparison was held on the measurement platform of the World Radiation Center (PMOD/WRC) in Davos, Switzerland, from 10 to 17 July 2014. The results of the blind intercomparison revealed that ASRMs, currently used for solar UV measurements, show a large variation in the quality of their solar UV measurements. Most of the instruments overestimate the erythema-weighted UV index – in particular at large solar zenith angles – due to stray light contribution in the UV-B range. The spectral analysis of global solar UV irradiance further supported the finding that the uncertainties in the UV-B range are very large due to stray light contribution in this wavelength range. In summary, the UV index may be detected by some commercially available ASRMs within 5 % compared to the world reference spectroradiometer, if well characterized and calibrated, but only for a limited range of solar zenith angles. Generally, the tested instruments are not yet suitable for solar UV measurements for the entire range between 290 and 400 nm under all atmospheric conditions.

scholarly journals First national intercomparison of solar ultraviolet radiometers in Italy

2011 ◽  
Vol 4 (3) ◽  
pp. 2789-2826 ◽  
Author(s):  
H. Diémoz ◽  
A. M. Siani ◽  
G. R. Casale ◽  
A. di Sarra ◽  
B. Serpillo ◽  
...  
Keyword(s):  
Environmental Protection Agency ◽  
Calibration Data ◽  
Uv Index ◽  
Uv Irradiance ◽  
Solar Uv ◽  
Solar Uv Irradiance ◽  
Field Intercomparison ◽  
Synchronized Measurements ◽  
First Time ◽  
Double Monochromator

Abstract. A blind intercomparison of ground-based ultraviolet (UV) instruments has been organized for the first time in Italy. The campaign was coordinated by the Environmental Protection Agency of Aosta Valley (ARPA Valle d'Aosta) and took place in Saint-Christophe (45.8° N, 7.4° E, 570 m a.s.l.), in the Alpine region, from 8 to 23 June 2010. It involved 8 institutions, 10 broadband radiometers, 2 filter radiometers and 2 spectroradiometers. Synchronized measurements of downward global solar UV irradiance at the ground were collected and the raw series were then individually processed by the respective operators on the basis of their own procedures and calibration data. The comparison was performed in terms of global solar UV Index and integrated UV-A irradiance against a well-calibrated double monochromator spectroradiometer as reference. An improved algorithm for comparing broadband data and spectra has been developed. For some instruments, we found average deviations ranging from −16 % up to 20 % relative to the reference and diurnal variations as large as 15 % even in clear days. Remarkable deviations also arose from instruments recently in operation and never involved in field intercomparison.

scholarly journals Measurements of UV irradiance within the area of one satellite pixel

2008 ◽  
Vol 8 (18) ◽  
pp. 5615-5626 ◽  
Author(s):  
P. Weihs ◽  
M. Blumthaler ◽  
H. E. Rieder ◽  
A. Kreuter ◽  
S. Simic ◽  
...  
Keyword(s):  
Ozone Monitoring Instrument ◽  
Short Term ◽  
Uv Index ◽  
Clear Sky ◽  
Uv Irradiance ◽  
Instantaneous Values ◽  
The Mean ◽  
The Difference ◽  
Sky Conditions ◽  
Better Than

Abstract. A measurement campaign was performed in the region of Vienna and its surroundings from May to July 2007. Within the scope of this campaign erythemal UV was measured at six ground stations within a radius of 30 km. First, the homogeneity of the UV levels within the area of one satellite pixel was studied. Second, the ground UV was compared to ground UV retrieved by the ozone monitoring instrument (OMI) onboard the NASA EOS Aura Spacecraft. During clear-sky conditions the mean bias between erythemal UV measured by the different stations was within the measurement uncertainty of ±5%. Short term fluctuations of UV between the stations were below 3% within a radius of 20 km. For partly cloudy conditions and overcast conditions the discrepancy of instantaneous values between the stations is up to 200% or even higher. If averages of the UV index over longer time periods are compared the difference between the stations decreases strongly. The agreement is better than 20% within a distance of 10 km between the stations for 3 h averages. The comparison with OMI UV showed for clear-sky conditions higher satellite retrieved UV values by, on the average, approximately 15%. The ratio of OMI to ground measured UV lies between 0.9 and 1.5. and strongly depends on the aerosol optical depth. For partly cloudy and overcast conditions the OMI derived surface UV estimates show larger deviation from the ground-based reference data, and even bigger systematic positive bias. Here the ratio OMI to ground data lies between 0.5 and 4.5. The average difference between OMI and ground measurements is +24 to +37% for partly cloudy conditions and more than +50% for overcast conditions.

Ozone monitoring instrument satellite UV irradiance product correction using a global aerosol climatology

2009 ◽  
Author(s):  
Antti Arola ◽  
S. Kazadzis ◽  
J. Kujanpää ◽  
A. Lindfors ◽  
A. Bais ◽  
...  
Keyword(s):  
Ozone Monitoring Instrument ◽  
Monitoring Instrument ◽  
Uv Irradiance ◽  
Ozone Monitoring
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