scholarly journals Variability of Solar UV Index in Nepal

2017 ◽  
Vol 12 (1) ◽  
pp. 114-119 ◽  
Author(s):  
Niranjan Prasad Sharma
Keyword(s):  
Data Analysis ◽  
Sea Level ◽  
Zenith Angle ◽  
Seasonal Variations ◽  
Cloud Cover ◽  
Solar Zenith Angle ◽  
Atmospheric Parameters ◽  
Uv Index ◽  
Uv Irradiance ◽  
Solar Uv

The paper presents the variability of solar UV index in main cities of Nepal. The latitude and longitude of the cities are (27.72°N, 85.32°E), ( 28.22°N, 83.32°E) and (26.45°N 87.27°E) are located at an elevation of 1350m, 800m and 72m respectively from the sea level. The NILU- UV irradiance meter of serial number (135, 137 and 133) was used to record UV radiation on these stations.  From the measurement and data analysis it was found that there were distinct diurnal, hourly mean and spring variations in the UV index. The UV index is primarily controlled by solar zenith angle for both the diurnal and seasonal variations. The highest values of hourly mean UV index was found at noon time in all seasons. Atmospheric parameters such as Solar Zenith angle (SZA), Cloud cover, aerosols  and Ozone contribute to the daily fuctuations in the UV Index. The UV Index was found to be 8.72, 9.9 and 9.2 in June 9, in Kathmandu (KTM), Pokhara (PKR) and Biratnagar (BRT).While the UV Index (UVI) in September 27 was found to be 8.52, 8.18 and 9.36 in KTM, PKR and BRT respectively. Daily mean highest UV Index before monsoon at PKR was found to be 10.6 and 8.98 at day number 144 and 100.Journal of the Institute of Engineering, 2016, 12(1): 114-119

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.

Impact of Cloud Cover on Solar Radiative Biases in Deep Convective Regimes

2005 ◽  
Vol 62 (6) ◽  
pp. 1989-2000 ◽  
Author(s):  
F. Di Giuseppe ◽  
A. M. Tompkins
Keyword(s):  
Zenith Angle ◽  
Cloud Cover ◽  
Solar Zenith Angle ◽  
Total Error ◽  
Three Dimensional ◽  
Bias Reduction ◽  
Total Cloud Cover ◽  
Correction Technique ◽  
Cloud Resolving Model ◽  
Path Direction

Abstract Conflicting claims have been made concerning the magnitude of the bias in solar radiative transfer calculations when horizontal photon transport is neglected for deep convective scenarios. The difficulty of obtaining a realistic set of cloud scenes for situations of complex cloud geometry, while certain characteristics such as total cloud cover are systematically controlled, has hindered the attempt to reach a consensus. Here, a simple alternative approach is adopted. An ensemble of cloud scenes generated by a cloud resolving model are modified by an idealized function that progressively alters the cirrus anvil coverage without affecting the realism of the scene produced. Comparing three-dimensional radiative calculations with the independent column approximation for all cloud scenes, it is found that the bias in scene albedo can reach as much as 22% when the sun is overhead and 46% at low sun angles. The bias is an asymmetrical function of cloud cover with a maximum attained at cirrus anvil cloud cover of approximately 30%–40%. With a cloud cover of 15%, the bias is half its maximum value, while it is limited for coverage exceeding 80%. The position of the peak occurs at the cloud cover coinciding with the maximum number of independent clouds present in the scene. Increasing the cloud cover past this point produces a decrease in the number of isolated clouds because of cloud merging, with a consequential bias reduction. With this systematic documentation of the biases as a function of total cloud cover, it is possible to identify two contributions to the total error: the geometrical consequences of the effective cloud cover increase at low sun angles and the true 3D scattering effect of photons deviating from the original path direction. An attempt to account for the former geometrical contribution to the 1D bias is made by performing a simple correction technique, whereby the field is sheared by the tangent of the solar zenith angle. It is found that this greatly reduces the 1D biases at low sun angles. Because of the small aspect ratio of the cirrus cloud deck, the remaining bias contribution is small in magnitude and almost independent of solar zenith angle.

scholarly journals Using a Parameterization of a Radiative Transfer Model to Build High-Resolution Maps of Typical Clear-Sky UV Index in Catalonia, Spain

2005 ◽  
Vol 44 (6) ◽  
pp. 789-803 ◽  
Author(s):  
Jordi Badosa ◽  
Josep-Abel González ◽  
Josep Calbó ◽  
Michiel van Weele ◽  
Richard L. McKenzie
Keyword(s):  
High Resolution ◽  
Radiative Transfer ◽  
Zenith Angle ◽  
Solar Zenith Angle ◽  
Absolute Error ◽  
Single Scattering ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Uv Index ◽  
Wide Range

Abstract To perform a climatic analysis of the annual UV index (UVI) variations in Catalonia, Spain (northeast of the Iberian Peninsula), a new simple parameterization scheme is presented based on a multilayer radiative transfer model. The parameterization performs fast UVI calculations for a wide range of cloudless and snow-free situations and can be applied anywhere. The following parameters are considered: solar zenith angle, total ozone column, altitude, aerosol optical depth, and single-scattering albedo. A sensitivity analysis is presented to justify this choice with special attention to aerosol information. Comparisons with the base model show good agreement, most of all for the most common cases, giving an absolute error within ±0.2 in the UVI for a wide range of cases considered. Two tests are done to show the performance of the parameterization against UVI measurements. One uses data from a high-quality spectroradiometer from Lauder, New Zealand [45.04°S, 169.684°E, 370 m above mean sea level (MSL)], where there is a low presence of aerosols. The other uses data from a Robertson–Berger-type meter from Girona, Spain (41.97°N, 2.82°E, 100 m MSL), where there is more aerosol load and where it has been possible to study the effect of aerosol information on the model versus measurement comparison. The parameterization is applied to a climatic analysis of the annual UVI variation in Catalonia, showing the contributions of solar zenith angle, ozone, and aerosols. High-resolution seasonal maps of typical UV index values in Catalonia are presented.

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 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 Utilising shade to optimize UV exposure for vitamin D

2008 ◽  
Vol 8 (11) ◽  
pp. 2841-2846 ◽  
Author(s):  
D. J. Turnbull ◽  
A. V. Parisi
Keyword(s):  
Zenith Angle ◽  
Vitamin D3 ◽  
Solar Zenith Angle ◽  
The Body ◽  
Uv Exposure ◽  
Diffuse Component ◽  
Spectral Measurements ◽  
Number Of Factors ◽  
Solar Uv ◽  
To Receive

Abstract. Numerous studies have stated that humans need to utilise full sun radiation, at certain times of the day, to assist the body in synthesising the required levels of vitamin D3. The time needed to be spent in the full sun depends on a number of factors, for example, age, skin type, latitude, solar zenith angle. Current Australian guidelines suggest exposure to approximately 1/6 to 1/3 of a minimum erythemal dose (MED), depending on age, would be appropriate to provide adequate vitamin D3 levels. The aim of the study was to determine the exposure times to diffuse solar UV to receive exposures of 1/6 and 1/3 MED for a changing solar zenith angle in order to assess the possible role that diffuse UV (scattered radiation) may play in vitamin D3 effective UV exposures (UVD3). Diffuse and global erythemal UV measurements were conducted at five minute intervals over a twelve month period for a solar zenith angle range of 4° to 80° at a latitude of 27.6° S. For a diffuse UV exposure of 1/3 MED, solar zenith angles smaller than approximately 50° can be utilised for exposure times of less than 10 min. Spectral measurements showed that, for a solar zenith angle of 40°, the UVA (315–400 nm) in the diffuse component of the solar UV is reduced by approximately 62% compared to the UVA in the global UV, whereas UVD3 wavelengths are only reduced by approximately 43%. At certain latitudes, diffuse UV under shade may play an important role in providing the human body with adequate levels of UVD3 (290–315 nm) radiation without experiencing the high levels of UVA observed in full sun.

scholarly journals UV variability in Moscow according to long-term UV measurements and reconstruction model

2008 ◽  
Vol 8 (12) ◽  
pp. 3025-3031 ◽  
Author(s):  
N. Y. Chubarova
Keyword(s):  
Seasonal Variations ◽  
Total Ozone ◽  
Cloud Amount ◽  
Point Of View ◽  
Atmospheric Parameters ◽  
Aerosol Loading ◽  
Uv Irradiance ◽  
The Impact ◽  
Reconstruction Model

Abstract. Long-term measurements of erythemally weighted UV irradiance (Qer) have been analyzed for the 1999–2006 period as well as UV variability according to a reconstruction model since 1968. The estimates of different atmospheric parameters effects, including NO2 content, on Qer have been obtained on seasonal and interannual scales. It has been shown that NO2 content in conditions of large megalopolis provides average Qer decrease of about 1.5–2%. The seasonal variations of the observed UV indices are discussed from the point of view of the impact on health. Using the reconstruction model we showed a distinct growth in Qer since 1980 due to changes in total ozone (+2.5% per decade), effective cloud amount transmission (+2.1% per decade) and aerosol loading (+1.1% per decade). However, there is no change in Qer over the longer 1968–2006 period due to significant decrease in effective cloud amount transmission (−11% per decade) in 1968–1980.

scholarly journals Measuring and Visualizing Solar UV for a Wide Range of Atmospheric Conditions on Hawai’i Island

2019 ◽  
Vol 16 (6) ◽  
pp. 997
Author(s):  
Forrest M. Mims III ◽  
Andrew J. S. McGonigle ◽  
Thomas C. Wilkes ◽  
Alfio V. Parisi ◽  
William B. Grant ◽  
...  
Keyword(s):  
Sea Level ◽  
Atmospheric Conditions ◽  
Solar Ultraviolet Radiation ◽  
Biomass Smoke ◽  
Uv Index ◽  
Mauna Loa ◽  
Wide Range ◽  
The Face ◽  
Extreme Uv ◽  
Solar Uv

: Hawai’i Island often receives extreme (UV Index ≥ 11) solar ultraviolet radiation (UVR). While the UV Index (UVI) has been measured since 1997 at Hawai’i’s high-altitude Mauna Loa Observatory (MLO), measurements where people live and recreate are rare. We measured UVI on the face of a rotating mannequin head with UVR sensors at its eyes, ears and cheeks while simultaneously measuring the UVI with a zenith-facing sensor at MLO and seven sites at or near sea level from 19 July to 14 August 2018. The mannequin sensors received higher UVR at midmorning and midafternoon than at noon. For example, at sea level the peak UVI at the left cheek was 5.2 at midmorning and 2.9 at noon, while the horizontal UVI at noon was 12.7. Our measurements were supplemented with wide-angle (190° and 360°) sky photographs and UV images of the mannequin head. Because the UVI applies to horizontal surfaces, people in tropical and temperate latitudes should be informed that their face may be more vulnerable to UVR at midmorning and midafternoon than at noon. Finally, our instruments provided opportunities to measure unexpected UVR-altering events, including rare biomass smoke over MLO and spectroscopic measurements of substantial UVR-absorbing sulfur dioxide in the eruption plume of the Kilauea volcano.

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