Validation of TROPOMI Surface UV Radiation Product

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolution for most data products is 7.2 x 3.5 km2 (5.6 x 3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development and processing of the TROPOMI Surface Ultraviolet (UV) Radiation Product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and antarctic areas were used for validation of TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate/UV index and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation results showed that for most sites 60–80 % of TROPOMI data was within ±20 % from ground-based data for snow free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow free surface daily doses were within ±10 % and ±5 % at two thirds and at half of the sites, respectively. At several sites more than 90 % of clear sky TROPOMI data were within ±20 % from ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values, but at high latitudes where non-homogeneous topography and albedo/snow conditions occurred, the negative bias was exceptionally high, from −30 % to −65 %. Positive biases of 10–15 % were also found for mountainous sites due to challenging topography. The TROPOMI Surface UV Radiation Product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain which can be used to filter the data retrieved under challenging conditions.

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Validation of the TROPOspheric Monitoring Instrument (TROPOMI) surface UV radiation product

Atmospheric Measurement Techniques ◽

10.5194/amt-13-6999-2020 ◽

2020 ◽

Vol 13 (12) ◽

pp. 6999-7024

Author(s):

Kaisa Lakkala ◽

Jukka Kujanpää ◽

Colette Brogniez ◽

Nicolas Henriot ◽

Antti Arola ◽

...

Keyword(s):

Free Surface ◽

Uv Radiation ◽

Atmospheric Composition ◽

Uv Index ◽

Finnish Meteorological Institute ◽

Monitoring Instrument ◽

Polar Orbiting Satellite ◽

Snow Conditions ◽

Relative Differences ◽

Meteorological Institute

Abstract. The TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor (S5P) satellite was launched on 13 October 2017 to provide the atmospheric composition for atmosphere and climate research. The S5P is a Sun-synchronous polar-orbiting satellite providing global daily coverage. The TROPOMI swath is 2600 km wide, and the ground resolution for most data products is 7.2×3.5 km2 (5.6×3.5 km2 since 6 August 2019) at nadir. The Finnish Meteorological Institute (FMI) is responsible for the development of the TROPOMI UV algorithm and the processing of the TROPOMI surface ultraviolet (UV) radiation product which includes 36 UV parameters in total. Ground-based data from 25 sites located in arctic, subarctic, temperate, equatorial and Antarctic areas were used for validation of the TROPOMI overpass irradiance at 305, 310, 324 and 380 nm, overpass erythemally weighted dose rate/UV index, and erythemally weighted daily dose for the period from 1 January 2018 to 31 August 2019. The validation results showed that for most sites 60 %–80 % of TROPOMI data was within ±20 % of ground-based data for snow-free surface conditions. The median relative differences to ground-based measurements of TROPOMI snow-free surface daily doses were within ±10 % and ±5 % at two-thirds and at half of the sites, respectively. At several sites more than 90 % of cloud-free TROPOMI data was within ±20 % of ground-based measurements. Generally median relative differences between TROPOMI data and ground-based measurements were a little biased towards negative values (i.e. satellite data < ground-based measurement), but at high latitudes where non-homogeneous topography and albedo or snow conditions occurred, the negative bias was exceptionally high: from −30 % to −65 %. Positive biases of 10 %–15 % were also found for mountainous sites due to challenging topography. The TROPOMI surface UV radiation product includes quality flags to detect increased uncertainties in the data due to heterogeneous surface albedo and rough terrain, which can be used to filter the data retrieved under challenging conditions.

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Possible values of UV index in Serbia

Srpski arhiv za celokupno lekarstvo ◽

10.2298/sarh0812640l ◽

2008 ◽

Vol 136 (11-12) ◽

pp. 640-643 ◽

Cited By ~ 1

Author(s):

Milorad Letic

Keyword(s):

Uv Radiation ◽

The Sun ◽

Total Column Ozone ◽

Uv Index ◽

Clear Sky ◽

Expected Values ◽

June July ◽

Column Ozone ◽

Ozone Column

INTRODUCTION UV Index is an indicator of human exposure to solar ultraviolet (UV) rays. The numerical values of the UV Index range from 1-11 and above. There are three levels of protection against UV radiation; low values of the UV Index - protection is not required, medium values of the UV Index - protection is recommended and high values of the UV Index - protection is obligatory. The value of the UV Index primarily depends on the elevation of the sun and total ozone column. OBJECTIVE The aim of the study is to determine the intervals of possible maximal annual values of the UV Index in Serbia in order to determine the necessary level of protection in a simple manner. METHOD For maximal and minimal expected values of total column ozone and for maximal elevation of the sun, the value of the UV Index was determined for each month in the Northern and Southern parts of Serbia. These values were compared with the forecast of the UV Index. RESULTS Maximal clear sky values of the UV Index in Serbia for altitudes up to 500m in May, June, July and August can be 9 or even 10, and not less than 5 or 6. During November, December, January and February the UV Index can be 4 at most. During March, April, September and October the expected values of the UV Index are maximally 7 and not less than 3. The forecast of the UV Index is within these limits in 98% of comparisons. CONCLUSION The described method of determination of possible UV Index values showed a high agreement with forecasts. The obtained results can be used for general recommendations in the protection against UV radiation.

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UV Index Forecasting under the Influence of Desert Dust: Evaluation against Surface and Satellite-Retrieved Data

Atmosphere ◽

10.3390/atmos11010096 ◽

2020 ◽

Vol 11 (1) ◽

pp. 96 ◽

Cited By ~ 1

Author(s):

Dillan Raymond Roshan ◽

Muammer Koc ◽

Amir Abdallah ◽

Luis Martin-Pomares ◽

Rima Isaifan ◽

...

Keyword(s):

Uv Radiation ◽

Mesoscale Model ◽

Dust Storms ◽

Average Error ◽

Accurate Estimation ◽

Strong Impact ◽

Uv Index ◽

Desert Dust ◽

Clear Sky ◽

Uv Irradiance

Human exposure to healthy doses of UV radiation is required for vitamin D synthesis, but exposure to excessive UV irradiance leads to several harmful impacts ranging from premature wrinkles to dangerous skin cancer. However, for countries located in the global dust belt, accurate estimation of the UV irradiance is challenging due to a strong impact of desert dust on incoming solar radiation. In this work, a UV Index forecasting capability is presented, specifically developed for dust-rich environments, that combines the use of ground-based measurements of broadband irradiances UVA (320–400 nm) and UVB (280–315 nm), NASA OMI Aura satellite-retrieved data and the meteorology-chemistry mesoscale model WRF-Chem. The forecasting ability of the model is evaluated for clear sky days as well as during the influence of dust storms in Doha, Qatar. The contribution of UV radiation to the total incoming global horizontal irradiance (GHI) ranges between 5% and 7% for UVA and 0.1% and 0.22% for UVB. The UVI forecasting performance of the model is quite encouraging with an absolute average error of less than 6% and a correlation coefficient of 0.93. In agreement with observations, the model predicts that the UV Index at local noontime can drop from 10–11 on clear sky days to approximately 6–7 during typical dusty conditions in the Arabian Peninsula—an effect similar to the presence of extensive cloud cover.

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Towards closure between measured and modelled UV under clear skies at four diverse sites

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-7-1507-2007 ◽

2007 ◽

Vol 7 (1) ◽

pp. 1507-1555 ◽

Cited By ~ 1

Author(s):

J. Badosa ◽

R. L. McKenzie ◽

M. Kotkamp ◽

J. Calbó ◽

J. A. González ◽

...

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Single Scattering ◽

Uv Spectra ◽

Atmospheric Composition ◽

Model Calculations ◽

Uv Index ◽

Mauna Loa ◽

Clear Sky ◽

One Year

Abstract. The purpose of this work is determine the extent of closure between measurements and models of UV irradiances at diverse sites using state of the art instruments, models, and the best available data as inputs to the models. These include information about aerosol optical depth (unfortunately not extending down as far into the UVB region as desirable because such information is not generally available), ozone column amounts, as well as vertical profiles of ozone and temperature. We concentrate on clear-sky irradiances, and report the results in terms of UV Index (UVI). Clear-sky data from one year of measurements at each of four diverse sites (Lauder – New Zealand, Mauna Loa Observatory – Hawaii, Boulder – Colorado, and Melbourne – Australia) have been analysed in detail, also taking account of different measurements of ozone, including satellite-derived values, as well as ground measured values, both from Dobson instruments and as retrieved from the UV spectra under study. Previous studies have generally focussed on data from a single site, and for shorter periods. Consequently, this study is the most comprehensive of its kind to date. At Lauder, which is the cleanest low altitude site, we obtained agreement between measurement and model at 5% level, which is consistent with the best agreement found previously. At Mauna Loa Observatory, similar agreement was achieved, but model calculations need to allow for reflections from cloud that are present below the observatory. At this site, there are occasional problems with using satellite-derived ozone. At Boulder, mean agreements were similar but the dispersion around the mean was slightly larger, corresponding to larger uncertainties in the aerosol inputs to the model. However, at Melbourne, which is the only non-NDACC (Network for the Detection of Atmospheric Composition Change) site, there remain unexplained discrepancies. The measured values are significantly lower than the calculated values. We investigate the extent to which this discrepancy can be explained by incomplete knowledge of aerosol extinctions in the UV at this site. We conclude that further information about aerosol optical depth and single scattering albedo in the UVB region is needed to resolve the issues. At the three NDACC sites, the closure provided by the study gives confidence in both the measurements and our ability to model them. The study revealed a limitation in the use of PTFE diffusers when temperatures are lower than approximately 20°C. It also documents the range of clear sky UVI values expected at these diverse sites.

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ERITEMINĖS ULTRAVIOLETINĖS SPINDULIUOTĖS POKYČIŲ ANALIZĖ

Sveikatos mokslai ◽

10.5200/sm-hs.2013.128 ◽

2013 ◽

Vol 23 (6) ◽

pp. 25-28 ◽

Cited By ~ 1

Author(s):

Renata Chadyšienė ◽

Aloyzas Girgždys

Keyword(s):

Uv Radiation ◽

Radiation Intensity ◽

Total Ozone ◽

Stratospheric Ozone ◽

Downward Trend ◽

Upward Trend ◽

Uv Index ◽

Clear Sky ◽

Ozone Data ◽

Very High

In this article the erythemally weighted UV radiation intensity variations during 2002-2011 were analysed. Also UV radiation intensity and total ozone data in this paper were analysed, because the UV index is directly dependent on the intensity of UV radiation, and most of the UV radiation is absorbed by stratospheric ozone. During 2002-2011 in the course of UV index - the upward trend was observed, and in the total ozone values - the downward trend was observed. During the investigated period in Lithuania the maximum UV index values (very high) on clear sky summer days were determined.

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Optimizing UV index determination from broadband irradiances

10.5194/gmd-2017-279 ◽

2017 ◽

Cited By ~ 1

Author(s):

Keith A. Tereszchuk ◽

Yves J. Rochon ◽

Chris A. McLinden ◽

Paul A. Vaillancourt

Keyword(s):

Radiative Transfer ◽

Root Mean Square ◽

Uv Radiation ◽

Relative Error ◽

Spectral Resolution ◽

High Spectral Resolution ◽

Mean Square ◽

Uv Index ◽

Clear Sky ◽

Sky Conditions

Abstract. Amidst mounting concerns about the depletion of stratospheric ozone (O3), and for subsequent increases in the surface irradiances of ultraviolet (UV) light and its effects on human health, a daily UV forecast program was launched by Environment Canada in 1993. The program serves to monitor harmful surface UV radiation and provide this information to the Canadian public through the UV index, a scale which reports the relative intensity of the Sun's UV radiation at the Earth's surface, and the corresponding protection actions to be taken. The UV index was accepted as a standard method of reporting surface UV irradiances by the World Meteorological Organization (WMO) and World Health Organization (WHO) in 1994. A study was undertaken to improve upon the prognosticative capability of Environment and Climate Change Canada's (ECCC) UV index forecast model. An aspect of that work, and the topic of this communication, was to investigate the use of the four UV broadband surface irradiance fields generated by ECCC's Global Environmental Multi-scale (GEM) numerical prediction model to determine the UV index. The basis of the investigation involves the creation of a suite of routines which employ high spectral resolution radiative transfer code developed to calculate UV index fields from GEM forecasts. These routines employ a modified version of the Cloud-J v7.4 radiative transfer model, which integrates GEM output to produce high spectral resolution surface irradiance fields. The output generated using the high-resolution radiative transfer code served to verify and calibrate GEM broadband surface irradiances under clear-sky conditions and their use in providing the UV index. A subsequent comparison of irradiances and UV index under cloudy conditions was also performed. Linear correlation agreement of surface irradiances from the two models for each of the two higher UV bands covering 310–330 nm and 330–400 nm is typically greater than 95 % for clear-sky conditions with associated root mean square relative errors of 5.5 % and 3.8 %. On the other hand, underestimations of clear-sky GEM irradiances were found on the order of ~30–50 % for the 294–310 nm band and by a factor of ~30 for the 280–294 nm band. This underestimation can be significant for UV index determination but would not impact weather forecasting. Corresponding empirical adjustments were applied to the broadband irradiances now giving a correlation coefficient of unity. From these, a least-squares fitting was derived for the calculation of the UV index. The resultant differences in UV indices from the high spectral resolution irradiances and the resultant GEM broadband irradiances are typically within 0.2 with a root mean square relative error in the scatter of ~5.5 % for clear-sky conditions. Similar results are reproduced under cloudy conditions with light to moderate clouds, having a relative error comparable to the clear-sky counterpart; under strong attenuation due to clouds, a substantial increase in the root mean square relative error of up to 30 % is observed due to differing cloud radiative transfer models.

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The effect of sun elevation, cloudiness, and altitude on the ultraviolet index in Czechia

Geografie ◽

10.37040/geografie.2021.001 ◽

2021 ◽

Vol 126 (2) ◽

pp. 1

Author(s):

Helena Tomanová ◽

Lucie Pokorná

Keyword(s):

Snow Cover ◽

Uv Radiation ◽

Stratospheric Ozone ◽

Meteorological Conditions ◽

Uv Index ◽

Clear Sky ◽

Negative Effect ◽

High Doses ◽

Definition Of ◽

Ultraviolet Index

Ultraviolet (UV) radiation has recently become an important topic in relation to the loss of stratospheric ozone. High doses of UV radiation have a negative effect on many organisms. This paper focuses on the UV index (UVI), which expresses the risk of UV radiation on human health. The aim of the paper is to describe the definition of UVI, and its measurement, and to summarize geographical parameters and meteorological conditions affecting the values of UVI. The effect of sun elevation, cloudiness, and altitude is demonstrated using observed data from the Hradec Králové, Košetice and Labská bouda stations during the period 2011–2017. The results show a strong effect of both sun elevation and cloudiness. The highest values of UVI (up to 8) are generally observed on sunny days around midday from May to July. The reduction of the UVI caused by clouds, fog, and rain is, on average, 85% of values typical for sunny days. The effect of altitude is distinctly weaker; a rise of UVI with increasing altitude is 0.4 per 1 km for clear sky and the surface without snow cover.

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Data flow of spectral UV measurements at Sodankylä and Jokioinen

10.5194/gi-2015-42 ◽

2016 ◽

Cited By ~ 1

Author(s):

J. S. Mäkelä ◽

K. Lakkala ◽

T. Koskela ◽

T. Karppinen ◽

J. M. Karhu ◽

...

Keyword(s):

Real Time ◽

Dead Time ◽

Stray Light ◽

Operational Control ◽

Uv Index ◽

Finnish Meteorological Institute ◽

Data Products ◽

Corrected Data ◽

Radiation Measurements ◽

Meteorological Institute

Abstract. We describe the steps that are used at the Finnish Meteorological Institute (FMI) to process spectral ultraviolet (UV) radiation measurements made with its three Brewer spectrophotometers, located in Sodankylä (67° N) and Jokioinen (61° N). The spectrum is measured many times a day, following a pre-programmed schedule. Multiple corrections are made to the data in near real time (dark current, dead time, stray light, noise spikes, temperature, and cosine correction) and quality control is also performed automatically. The Brewers are integrated into the operational control systems at FMI, allowing both quick responses to malfunctions and quick dissemination of the data products. Several data products are produced, including the near-real-time UV index and various daily dosages. The daily doses are calculated each morning for the previous day's data. Once per year the responses of the Brewers are recalculated, and the corrected data are uploaded to the European UV database hosted by FMI.

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Enhancement of UV Radiation by Cloud Effect in NE of Brazil

International Journal of Photoenergy ◽

10.1155/2017/8107435 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

Chigueru Tiba ◽

Sérgio da Silva Leal

Keyword(s):

Solar Radiation ◽

Uv Radiation ◽

Extreme Values ◽

Biological Effects ◽

Global Solar Radiation ◽

Seasonal Effect ◽

Enhancement Effect ◽

Monthly Basis ◽

Uv Index ◽

Clear Sky

This paper reports a detailed analysis of ground-based measurements of cloud-enhanced global solar and UV radiation in NE Brazil in the city of Recife. It was found that (a) the phenomenon of UV enhancement, above clear sky model, is not uncommon and that it occurs on at least eight months; (b) the cumulative duration can reach 13 minutes; (c) there is a clear seasonal effect, and the probability of occurrence on a monthly basis shows two peaks, one in March and another in October; and (d) the most extreme UV radiation was 70.4 W/m2, approximately 6 W/m2 higher than the clear sky UV radiation. The extreme values should be taken into account in the study of effects related to the UV index and biological effects. Two statistical models also were elaborated, to estimate the UV solar radiation, in which the first is for all sky conditions and the second exclusively for situations where the global solar radiation is equal to or higher than 1367 W/m2, resulting from the enhancement effect caused by a particular configuration of the clouds. The statistical indicatives for both models presented, respectively, MBE% of 3.09 and 0.48% and RMSE% of 15.80 and 3.90%.

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UV radiation measurements in Marambio, Antarctica during years 2017–2019 in a wider temporal and spatial context

10.5194/acp-2019-896 ◽

2019 ◽

Cited By ~ 1

Author(s):

Margit Aun ◽

Kaisa Lakkala ◽

Ricardo Sanchez ◽

Eija Asmi ◽

Fernando Nollas ◽

...

Keyword(s):

Uv Radiation ◽

Stratospheric Ozone ◽

Polar Vortex ◽

Early Summer ◽

Uv Index ◽

Finnish Meteorological Institute ◽

Time Period ◽

Temporal And Spatial ◽

Radiation Measurements

Abstract. In March 2017, ultraviolet (UV) radiation measurements with a multichannel GUV-2511 radiometer were started in Marambio, Antarctica (64.23º S; 56.62º W), by the Finnish Meteorological Institute (FMI) in collaboration with the Argentinian National Meteorological Service (SMN). These measurements were analysed and the results were compared to previous measurements at the same site with NILU-UV radiometer during 2000–2008 and to data from five stations across Antarctica. Measurements in Marambio showed lower UV radiation levels in 2017/2018 compared to those measured during 2000–2008. Also at several other stations in Antarctica the radiation levels were below average in that period. The maximum UV index (UVI) in Marambio was only 6.2, while, during the time period 2000–2008, the maximum was 12. In 2018/2019, the radiation levels were higher than in the previous year and the maximum UVI recorded in Marambio was 9.5. In Marambio, the largest variation of the UV radiation are during the spring and early summer when the stratospheric ozone concentration is at a minimum (the so-called ozone hole). Beside cloud cover, the strength of the polar vortex and the stratospheric ozone depletion are the primary factors that influence the surface UV radiation levels in Antarctica. As the recovery of the ozone layer is slow, the continuation of the measurements is crucial in order to be able to detect long-term changes in UV levels in Antarctica.

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