Method for retrieval of aerosol optical depth from multichannel irradiance measurements.

We present, to the best of our knowledge, a new method for retrieval of aerosol optical depth from multichannel irradiance measurements. A radiative transfer model is used to simulate measurements to create the new aerosol optical depth retrieval method. A description of the algorithm, simulations, proof of principle, merits, possible future developments and implementations is provided. As a demonstration, measurements in the New York City area are simulated based on the specific channel configuration of an existing multichannel irradiance instrument. Verification of the method with irradiance measurement data is also provided.

Validation of OMI-DOAS total ozone column amounts against ground-based measurements at an African equatorial belt site.

The total ozone column amount (TOCA) values from the Ozone Monitoring Instrument (OMI) derived from OMI/Aura ozone (O3) differential optical absorption spectroscopy (DOAS) V003 (OMDOAO3) have been validated against the ground-based TOCA values derived from Dobson and the Norwegian Institute for Air Research UV measurements in Kampala (0.31º N, 32.58º E, 1200 m), Uganda, for the period between 2005 and 2018. Under all-sky conditions, the OMI retrieval algorithm was found to underestimate the TOCA values with mean bias (MnB), root mean square error (RMSE), and correlation coefficient (r) values ranging from about -3.4% to -1.7%, 2.4% to 4.9%, and 0.73 to 0.90, respectively. When only days with a radiation modification factor greater than or equal to 65% were considered, the MnB, RMSE, and r values between TOCA values derived from ground-based and OMI measurements improved, and they ranged from -2.5% to -1.3%, 1.4% to 3.8%, and 0.8 to 0.91, respectively. A good agreement was found between TOCA values derived from Dobson measurements and those derived from OMI satellite measurements with MnB, RMSE, and r values of about -1.8%, 1.4%, and 0.91, respectively. This was due to the fact that Dobson measurements were taken only when the sky was perceived clear. The underestimation of TOCA values by the OMI retrieval algorithm was found to be due mainly to clouds and aerosols.

Ground-based measurements of total ozone column amount with a multichannel moderate-bandwidth filter instrument at the Troll research station, Antarctica.

Combining information from several channels of the Norwegian Institute for Air Research (NILU-UV) irradiance meter, one may determine the total ozone column (TOC) amount. A NILU-UV instrument has been deployed and operated on two locations at Troll research station in Jutulsessen, Queen Maud Land, Antarctica, for several years. The method used to determine the TOC amount is presented, and the derived TOC values are compared with those obtained from the Ozone Monitoring Instrument (OMI) located on NASA's AURA satellite. The findings show that the NILU-UV TOC amounts correlate well with the results of the OMI and that the NILU-UV instruments are suitable for monitoring the long-term change and development of the ozone hole. Because of the large footprint of OMI, NILU-UV is a more suitable instrument for local measurements.

UV Index monitoring in Europe.

The UV Index was established more than 20 years ago as a tool for sun protection and health care. Shortly after its introduction, UV Index monitoring started in several countries either by newly acquired instruments or by converting measurements from existing instruments into the UV Index. The number of stations and networks has increased over the years. Currently, 160 stations in 25 European countries deliver online values to the public via the Internet. In this paper an overview of these UV Index monitoring sites in Europe is given. The overview includes instruments as well as quality assurance and quality control procedures. Furthermore, some examples are given about how UV Index values are presented to the public. Through these efforts, 57% of the European population is supplied with high quality information, enabling them to adapt behaviour. Although health care, including skin cancer prevention, is cost-effective, a proportion of the European population still doesn't have access to UV Index information.

Daily, seasonal, and latitudinal variations in solar ultraviolet A and B radiation in relation to vitamin D production and risk for skin cancer.

BACKGROUND: Solar ultraviolet (UV) radiation varies with latitude, time of day, and season. Both spectral UV composition and ambient UV dose lead to different health outcomes at different latitudes. Finding the optimal time for sun exposure, whereby the positive effects of UV exposure (vitamin D) are facilitated and the negative effects (skin cancer, photoimmunosuppression) avoided are the most important consideration in modern skin cancer prevention programs. OBJECTIVES: This paper focuses on the latitude dependency of UVB, UVA, vitamin D production, and skin cancer risk in Caucasians. METHODS: Biologically effective UVB (280-315 nm) and UVA (315-400 nm) doses were calculated using radiative transfer models with appropriate climatologic data for selected locations. Incidences of squamous cell carcinoma (SCC) and cutaneous melanoma (CM) were retrieved from cancer registries and published articles. RESULTS: Annual doses of UVA radiation decrease much less with increasing latitude than annual doses of UVB. Incidences of CM also decrease less steeply with increasing latitude than incidences of SCC. As SCC is caused mainly by UVB, these observations support the assumption that UVA plays an important role in the development of CM. The variations in UVA (relevant to CM) and UVB (relevant to vitamin D production) over 1 day differ: the UVB : UVA ratio is maximal at noon. CONCLUSIONS: The best way to obtain a given dose of vitamin D with minimal carcinogenic risk is through a non-burning exposure in the middle of the day, rather than in the afternoon or morning.

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

The Ozone Monitoring Instrument (OMI) overpass solar ultraviolet (UV) indices have been validated against the ground-based UV indices derived from Norwegian Institute for Air Research UV measurements in Kampala (0.31° N, 32.58° E, 1200 m), Uganda for the period between 2005 and 2014. An excessive use of old cars, which would imply a high loading of absorbing aerosols, could cause the OMI retrieval algorithm to overestimate the surface UV irradiances. The UV index values were found to follow a seasonal pattern with maximum values in March and October. Under all-sky conditions, the OMI retrieval algorithm was found to overestimate the UV index values with a mean bias of about 28%. When only days with radiation modification factor greater than or equal to 65%, 70%, 75%, and 80% were considered, the mean bias between ground-based and OMI overpass UV index values was reduced to 8%, 5%, 3%, and 1%, respectively. The overestimation of the UV index by the OMI retrieval algorithm was found to be mainly due to clouds and aerosols.

Vitamin D and ultraviolet phototherapy in Caucasians.

Ultraviolet B (UVB) radiation increases vitamin D level, but the influence of different UV sources (broadband and narrowband UVB lamps, solar simulators and sunbeds) and exposure durations have not been well characterized. In this study the influence of different UV sources on serum 25-hydroxyvitamin-D3 (25(OH)D3) levels in humans are reviewed. Serum 25(OH)D levels before and after UV exposure, and UV doses were extracted from 18 papers published in the past eight years. It was found that the UV dose-response curve for vitamin D generation in humans, as measured by the increments of serum 25(OH)D, is not linear with increasing UV doses and reaches a plateau at about 55 nmol/L after 4-5 weeks. About a half of this increase is equal to the difference between winter and summer 25(OH)D levels, and may be reached after 23 SEDs. The increments decrease with increasing baseline concentration of serum 25(OH)D, and the efficiency of only 0.7 nmol/L per SED is expected on the average when initial concentrations are higher than 50-60 nmol/L. A whole body exposure to 2 SEDs of UVB radiation 3 times per week is expected to rise serum 25(OH)D with an initial rate of 3.9 nmol/L per SED, bringing a winter level of serum 25(OH)D up to a summer level.

The relationship between UV exposure and incidence of skin cancer.

BACKGROUND: The incidence rates of skin cancer increase with decreasing latitude in most western countries. Ultraviolet (UV) radiation is a main risk factor for skin cancer. METHODS: We have studied the relationship between UV exposure and skin cancer incidence rates of squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and cutaneous melanoma (CM), and tried to fit different mathematical models to the experimental data. RESULTS: The incidence-UV exposure relationship for all three cancers is best described by the power law: ln(RTD) = Ab ·ln(annual UVEry dose), with relative tumor density (RTD) being age-adjusted incidence rate per unit area of skin, and the power parameter Ab being the biological amplification factor. For SCC, the RTD is a factor of 16-19 times larger on the head than on the trunk. For BCC, this factor is 7 and for CM it is 0.9-1.3. Ab for CM has remained almost unchanged from the 1960s until recently. CONCLUSIONS: The incidence-sun exposure relationship for all three cancers is well described by the power law. SCC is dependent on total UV exposures, while BCC, and even more CM, is dependent also on exposure patterns, with intermittent exposures being most carcinogenic.

New neural-network-based method to infer total ozone column amounts and cloud effects from multi-channel, moderate bandwidth filter instruments.

A new method is presented based on a radial basis function neural network (RBF-NN) to analyze data obtained by ultraviolet (UV) irradiance instruments. Application of the RBF-NN method to about three years of data obtained by a NILU-UV device, which is a multi-channel, moderate bandwidth filter instrument, revealed that compared to the traditional Look-up table (LUT) method, the RBF-NN method yielded better agreement with a 1% decrease in relative difference and an increase of 0.03 in correlation with total ozone column (TOC) values obtained from the Ozone Monitoring Instrument (OMI). Furthermore, the RBF-NN method retrieved more valid results (daily average values within a meaningful range (200-500 DU)) than the LUT method. Compared with RBF-NN retrievals, TOC values obtained from the OMI are underestimated under cloudy conditions. This finding agrees with conclusions reached by Anton and Loyola (2011).

Ultraviolet radiation and cutaneous malignant melanoma.

Essential features of the epidemiology and photobiology of cutaneous malignant melanoma (CMM) in Norway were studied in comparison with data from countries at lower latitudes. Arguments for and against a relationship between ultraviolet radiation (UV) from sun and artificial light and CMM are discussed. Our data indicate that UV is a carcinogen for CMM and that intermittent exposures are notably melanomagenic. This hypothesis was supported both by latitude gradients, by time trends and by changing patterns of tumor density on different body localizations. However, even though UV radiation generates CMM, it may also have a protective action and/or an action that improves prognosis. There appears to be no, or even an inverse latitude gradient for CMM arising on non-UV exposed body localizations (uveal melanoma, CMMs arising in the vulva, perianal/anorectal regions, etc.). Furthermore, CMM prognosis was gradually improved over all years of increasing incidence (up to 1990), but during the past 20 years, incidence rates stabilized and prognosis was not improved significantly. Comparisons of skin cancer data from Norway, Australia and New Zealand indicate that squamous cell carcinoma and basal cell carcinoma are mainly related to annual solar UVB fluences, while UVA fluences play a larger role of CMM.

Ultraviolet-radiation and health: optimal time for sun exposure.

Positive as well as negative health effects of exposure of human skin to UV radiation depend on spectra and fluence rates, both of which being dependent on latitude, time of the day and several other factors. The major positive effects are related to vitamin D photosynthesis and the major negative effect is skin cancer development. The action spectra for these effects are different. This lead us to conclude that for optimal vitamin D synthesis at minimal risk of cutaneous malignant melanoma (CMM), the best time for sun exposure is between 10 a.m. and 1 p.m. Thus, the common health recommendation (that sun exposure should be avoided between the hours of 10 a.m. and 4 p.m. and postponed to the afternoon) may be wrong.

Aerosols in coastal and inland areas in the equatorial African belt.

Aerosols affect the climate directly through absorption and reflection of sunlight back to space and indirectly by acting as cloud condensation nuclei. This paper is based on more than three decades of satellite data (1979-1994 and 1996-2012) from total ozone mapping spectrometer (TOMS) and ozone monitoring instrument (OMI), which have provided measurements of backscattered radiances in the wavelength range from 331 to 380 nm. These data have been used to determine the aerosol climatology and to investigate the influence of the aerosol index (AI) on the ultraviolet index (UVI) in coastal land areas in Serrekunda (13.28°N, 16.34°W), The Gambia, and Dar-es-Salaam (6.8°S, 39.26°E), Tanzania, as well as in inland areas in Kampala (0.19°N, 32.34°E), Uganda. Heavy aerosol loadings were found to occur in the dry seasons at all three locations. To reduce the influence of clouds, we disregarded TOMS and OMI data for days during which the UV reflectivity was larger than 9% and investigated the correlation of the AI with the UVI for the remaining days at the three locations. We found a high correlation coefficient of 0.82 for Serrekunda, but poor correlation for Kampala and Dar-es-Salaam. The average AI for Serrekunda was found to be about three times higher than that for Kampala or Dar-es-Salaam, and a positive trend was found for the AI in Kampala and Dar-es-Salaam, whereas a negative trend was found for the AI in Serrekunda.

Comparison of ground-based measurements of solar UV radiation at four sites on the Tibetan Plateau.

We compare results for the UV index (UVI), the total ozone column (TOC), and the radiation modification factor (RMF, being 1 in the absence of clouds and aerosols) at four sites on the Tibetan Plateau. The results were obtained by analyzing ground measurements by multichannel moderate-bandwidth filter instruments for the period July 2008-September 2010, and radiative transfer modeling was used to aid the interpretation of the results. The highest UVI of 20.6 was measured in Tingri (28.7°N; 4335 m). For July, monthly mean UVI values were 14.5 and 12.9 in Tingri and Lhasa (29.7°N; 3683 m), respectively. Generally, the UVI levels in Tingri and Lhasa were higher than in Nagchu (31.5°N; 4510 m) and Linzhi (29.7°N; 2995 m), due to less cloud cover at the former two sites. In 2009, the annual mean UVI and RMF values were 6.8 and 0.7 for Linzhi, 8.8 and 0.92 for Lhasa, 10.5 and 0.92 for Tingri, and 6.7 and 0.7 for Nagchu. Radiative transfer simulations indicate that the latitude difference would correspond to an increase in the UVI of about 0.3 from Nagchu to Tingri; whereas, the altitude difference would correspond to a reduction of about 1.5%, implying that the observed difference is due to the difference in cloud cover. The annual mean TOC values were found to be 260-264 Dobson units (DU) in Lhasa, Linzhi, and Nagchu, and 252 DU in Tingri. TOC values in Lhasa were found to agree within 3% with those derived from Ozone Monitoring Instrument (OMI) measurements.

Biologically efficient solar radiation: Vitamin D production and induction of cutaneous malignant melanoma.

Solar ultraviolet (UV) radiation is the main source of vitamin D production and is also the most important environmental risk factor for cutaneous malignant melanoma (CMM) development. In the present study the relationships between daily or seasonal UV radiation doses and vitamin D status, dietary vitamin D intake and CMM incidence rates at different geographical latitudes were investigated. North-South gradients of 25-hydroxyvitamin D (25(OH)D) generation and CMM induction were calculated, based on known action spectra, and compared with measured vitamin D levels and incidence rates of CMM. The relative roles of UVA and UVB in CMM induction are discussed. Latitudinal dependencies of serum 25(OH)D levels and CMM incidence rates can only partly be explained by ambient UV doses. The UV sensitivity is different among populations with different skin color. This is well known for CMM, but seems also to be true for vitamin D status. The fact that UV-induced vitamin D may reduce the risk of CMM complicates the discussion. To some extent high dietary vitamin D intake seems to compensate low UV doses.

North-South gradients of melanomas and non-melanomas: A role of vitamin D?

Incidence rates of skin cancer increase with decreasing latitude in Norway, as in many other countries with white populations. The latitudinal trends of the incidence rates of skin cancer were studied and compared with data for vitamin D-induced by UV and for vitamin D intake. The north-south gradient for CMM incidence rates on sun exposed skin is much smaller than those for BCC and SCC, and that for BCC is smaller than that for SCC. This indicates that SCC and BCC are mainly due to solar UVB, while UVA may play a significant role for CMM and a smaller role for BCC, since the north-south gradient of annual UVB fluences is larger than that of UVA fluences. However, there is an inverse latitudinal gradient of skin cancer in central Europe. This is probably due to a gradient of skin color, since white skin is an important determinant of increased risk of skin cancer. The role of vitamin D for skin cancer risk is difficult to evaluate, since serum levels of 25-hydroxyvitamin D, as well as vitamin D intakes, are widely different from country to country. Still, epidemiological evidence indicates a role: for melanomas arising on non-sun exposed body localizations (uveal melanomas, melanomas arising in the vulva and perianal/anorectal regions) there appears to be no latitudinal gradient, or, a negative gradient, i.e., increasing rates with decreasing latitude as would be expected if UV-generated vitamin D plays a protective role. Both skin cancer risk and vitamin D photosynthesis decrease with increasing skin darkness.

Vitamin D status in healthy Romanian caregivers and risk of respiratory infections.

OBJECTIVES: To investigate the vitamin D status during winter of a healthy population of hospital employees and to assess the correlation between vitamin D status and risk of infections in the upper respiratory tract. DESIGN: One hundred and ten healthy volunteers answered a questionnaire on their solar exposure habits and vitamin D intake and delivered one blood sample for quantification of vitamin D level (serum 25-hydroxyvitamin D (25(OH)D) concentration) during December 2007-January 2008. At the end of the winter we screened for the occurrence of respiratory infections and sought associations with vitamin D status. SETTING: Bucharest, Romania, 45°N. SUBJECTS: One hundred and ten healthy hospital employees. RESULTS: Eighty per cent of participants were vitamin D deficient (25(OH)D level below 50 nmol/l). The main determinant of serum 25(OH)D was sun exposure during the summer previous to the study (P = 0·02 in multivariate analysis). Intake of vitamin D, BMI and age played no significant role for the level of 25(OH)D. Overall we found a non-significant negative correlation between 25(OH)D level and new cases of infection (Spearman correlation coefficient of -0·12, P = 0·2). CONCLUSIONS: Vitamin D status is alarmingly poor in active, relatively young women residing in Romania. If our results are reproduced by other investigations, action to improve vitamin D status at the population level is necessary. We were not able to show a statistically significant relationship between vitamin D status and infection risk in our material.

UVA, UVB and incidence of cutaneous malignant melanoma in Norway and Sweden.

Latitudinal dependencies of UVA and UVB were studied together with relevant epidemiological data for squamous cell carcinoma (SCC) and cutaneous malignant melanoma (CMM) in Norway and Sweden. Our data support the hypothesis that solar UVA radiation may play a role for CMM induction. The etiologies of SCC and CMM are different according to a latitudinal dependency and differences in age curves. Sun exposure patterns, age-related decay rates of repair of UV damage and sex hormones may play different roles for the two skin cancers. Also, UVB induction of vitamin D may be involved. CMM incidence rates among young people have decreased or been constant since about 1990 in Norway and Sweden. All reasons for UVA contributing to CMM will be discussed.

The seasonality of pandemic and non-pandemic influenzas: the roles of solar radiation and vitamin D.

OBJECTIVES: Seasonal variations in ultraviolet B (UVB) radiation cause seasonal variations in vitamin D status. This may influence immune responses and play a role in the seasonality of influenza. METHODS: Pandemic and non-pandemic influenzas in Sweden, Norway, the USA, Singapore, and Japan were studied. Weekly/monthly influenza incidence and death rates were evaluated in view of monthly UVB fluences. RESULTS: Non-pandemic influenzas mostly occur in the winter season in temperate regions. UVB calculations show that at high latitudes very little, if any, vitamin D is produced in the skin during the winter. Even at 26°N (Okinawa) there is about four times more UVB during the summer than during the winter. In tropical regions there are two minor peaks in vitamin D photosynthesis, and practically no seasonality of influenza. Pandemics may start with a wave in an arbitrary season, while secondary waves often occur the following winter. Thus, it appears that a low vitamin D status may play a significant role in most influenzas. CONCLUSIONS: In temperate latitudes even pandemic influenzas often show a clear seasonality. The data support the hypothesis that high fluences of UVB radiation (vitamin D level), as occur in the summer, act in a protective manner with respect to influenza.

Where the sun does not shine: is sunshine protective against melanoma of the vulva?

Intermittent sun exposure and sunburn are strong predictors of cutaneous malignant melanoma (CMM). On the other hand, melanomas may arise also in non-sun-exposed areas such as the vulva. However, little is known about a possible relationship between sun exposure and vulvar melanoma. Temporal and latitudinal dependencies of the incidence rates of vulvar melanoma were studied in comparison with those of CMM among Caucasians in Sweden, East Germany, USA and Victoria (Australia). The ratios of vulvar melanoma incidence rates to those of CMM tend to decrease with increasing CMM rates. The incidence rates of CMM have increased with time until recently, while those of vulvar melanoma have either decreased or remain constant. In USA vulvar melanoma incidence rates seem to increase from south to north, while for CMM incidence rates on sun exposed skin areas decrease from south to north. Comparison of latitudinal trends of the incidence rates of vulvar melanomas and CMM show opposite trends. Whenever CMM rates increase, either with time or with decreasing latitude (indicating increased sun exposure) the ratio of vulvar melanoma rates to CMM rates on exposed skin, seem to decrease. Thus, latitudinal trends seem to support the assumption that vulvar melanomas are not generated by UV radiation, and the possibility exists that solar UV radiation, probably via its role in vitamin D photosynthesis in exposed skin, may have a protective effect against vulvar melanoma and should be further investigated.

Influence of narrowband UVB phototherapy on vitamin D and folate status.

BACKGROUND: A variety of studies have shown beneficial effects of different types of phototherapy in skin disorders. Such therapy leads to enhanced cutaneous vitamin D synthesis, which may be one of the mechanisms of action. Furthermore, another nutrient, folate, can probably also be influenced by UV radiation. OBJECTIVE: The aim of our study was to investigate the influence of low-dose narrowband UVB (nUVB) phototherapy of patients with psoriasis, atopic eczema and other skin disorders on serum levels of 25(OH) vitamin D (the serum marker for vitamin D status) and on serum and erythrocyte-folate. METHODS: 25(OH) vitamin D (25(OH)D), serum and erythrocyte-folate levels were measured before and after low-dose nUVB (TL-01 tubes) phototherapy of these patients. The spectrum of the TL-01 tube was compared with the solar spectrum, and the efficiency spectra of vitamin D photosynthesis were calculated. RESULTS: For patients with a high initial 25(OH)D serum level (> 80 nmol/l), no significant (P = 0.36) increase in 25(OH)D levels was seen, in contrast to patients with a low initial level (< 80 nmol/l) where a significant increase (P < 0.001) was observed. The increase was 30-60%, depending on the UVB dose (2.35-13.4 J/cm(2)). No significant nUVB-effect was found on the erythrocyte and serum-folate level. CONCLUSION: Low-dose nUVB treatment gives a significant increase (P < 0.001) of the vitamin D status in persons with low initial levels of 25(OH)D, but no effect on the folate level.