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 Validation of Satellite Estimated Solar Ultraviolet Radiation Data with Ground Based data in Kathmandu, Nepal

2016 ◽  
Vol 11 (1) ◽  
pp. 101-107
Author(s):  
Niranjan Prasad Sharma
Keyword(s):  
Ultraviolet Radiation ◽  
Scattered Light ◽  
Visible Spectrum ◽  
Relative Difference ◽  
Ozone Monitoring Instrument ◽  
Solar Ultraviolet Radiation ◽  
Radiation Data ◽  
Uv Irradiance ◽  
Relative Differences ◽  
Solar Ultraviolet

The main objective of this study is to validate the satellite estimated solar Ultraviolet radiation data with ground based data in  Kathmandu (27.72 N, 85.32 E), located at an elevation of 1350m,  from the sea level. The ground based measurement 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 0 0 radiometer designed to measure hemispherical irradiances on a fat surface. Meanwhile the Ozone Monitoring Instrument (OMI) on board, the NASA EOS Aura space craft is a nadir viewing spectrometer that measures solar refected and back scattered light in ultraviolet and visible spectrum. The study is based on OMI and ground based (GB), Ultraviolet Radiation (UVR) data. Considering these data the relative differences between predicted OMI and ground based Ultraviolet Index (UVI) assuming normal distribution ±1σ was found to be 24.8±13.7% in July. Further study showed that the ratio of predicted OMI, UVI to that determined from ground based measurement is 1.14. Also the relative difference in UVI in corrected condition in summer season was found to be 5.8%. The correlation between predicted UVI and ground based UVI was found to be signifcant. Journal of the Institute of Engineering, 2015, 11(1): 101-107

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

Validation of ozone monitoring instrument ultraviolet index against ground-based UV index in Kampala, Uganda

2015 ◽  
Vol 54 (28) ◽  
pp. 8537 ◽  
Author(s):  
Dennis Muyimbwa ◽  
Arne Dahlback ◽  
Taddeo Ssenyonga ◽  
Yi-Chun Chen ◽  
Jakob J. Stamnes ◽  
...  
Keyword(s):  
Ozone Monitoring Instrument ◽  
Uv Index ◽  
Monitoring Instrument ◽  
Ozone Monitoring ◽  
Ultraviolet Index

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.

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.

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