UV in the Polar Regions

The expansion of the Antarctic polar vortex during the 1990s, both in spatial and temporal extent into early summer, has increased the frequency of elevated UV-B episodes over sub-Antarctic populated areas (Rousseaux et al., 1999). These episodes are no longer just small pockets of ozone depleted stratospheric air coming from the break-up of the polar vortex, but include occasional excursions of the polar vortex edge over Ushuaia, Argentina and Punta Arenas, Chile. This occurred 44 times in the...

The Fore Optics

A 45 fused quartz prism is located at the head of the fore-optics tube and reflects incoming radiation (by total internal reflection) at right angles along the horizontal optical path of the instrument. The zenith prism plays an important role in selecting the appropriate source of radiation for lamp tests, sky measurements, direct sun or moon measurements, or UV spectral measurements. The prism rotates about the optical axis of the fore-optics so that radiation originating from zenith angles...

Study

A study by Barnard (2001) shows that specific air pollutants can reduce the increased surface levels of UV radiation, and offers an explanation for why the expected surface UV increases, caused by decreases in stratospheric ozone, have not been observed, especially in urban regions. Air pollution data (NOX, O3, PM-10, SO2) collected from an EPA UV monitoring site at the University of California at Riverside (UCR), combined with data from a site operated by the California Air Resources Board in...

UVB Absorbing Compounds and Leaf Pigments

The 2004 greenhouse study evaluated UV-B absorbing compounds and leaf pigment concentrations after 23.4 kJ m-2 UV-Bbe of exposure. The initial content of UV-B absorbance of acidified methanolic leaf extracts of Essex at 300 nm - 320 nm Figure 16.8 Changes in water use efficiency with UV exposure. Differences indicated are UV-Control. Error bars are standard error of the difference. All measurements were made in greenhouse experiments was higher than in Williams 82 and Essex had significantly...

I0l

In represents the photon counts measured by the Brewer at wavelength A and corresponds to the photon counts that would be measured at the top of the earth's atmosphere. The sum of aerosol and gas extinction is Tx and m is the air mass defined as the cosecant of the solar zenith angle. Once the I0 has been characterized, the total atmospheric optical depth (ra,x), at a specific wavelength, is calculated using the following Ii is the Brewer photon count as measured by the PS routine. The natural...

UV Dosimetry and Minimization Strategies

UV radiation incident on the earth's surface is comprised of both a direct component and a diffuse component. The combination of the diffuse and direct UV is termed the global UV. As the direct component is incident directly from the sun, it is easier to minimize by simply blocking its path. However, the diffuse UV component is incident from all directions due to atmospheric and environmental scattering and can constitute a significant proportion of the UV exposure to the human body. The...

McMurdo Station

McMurdo is affected by the ozone hole from September until early December (Fig. 3.6(a)). The maximum UV Index was 7.6 and occurred in November UV Indices measured after the solstice were below 5.5. The 90th percentile also exhibits a distinct maximum in late November. The average UV Index is fairly symmetric within 40 days about the solstice, but the 10th percentile is lower in the spring than in the summer. This feature is again a consequence of the Brewer- Dobson circulation. Historical UV...

Calculating RAF0

If the RAF is calculated directly from the power law definition F1 F2 (A A)RAF or RAF ln(F1 F2) ln(. 2 i), the result will have a dependence on ozone amount for any range of Q relative to the reference amount (Fig. 5.A1). In this study, the RAF is calculated as the best fit to the function i)RAF with the requirement that U is approximately 1 (Fig. 5.A2). This approximation works well for the entire range of SZA (Fig. 5.A3), the ozone range 200 DU to 600 DU, and for all four action spectra...

Radiative Transfer in the Coupled Atmosphere SnowIce Ocean Casio System Review of Modeling Capabilities

12 2 Knut Stamnes , Borge Hamre , and Jakob J. Stamnes 1 Light and Life Laboratory, Department of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken, NJ 07030, USA E-mail Knut.Stamnes stevens.edu 2 Department of Physics and Technology, University of Bergen, Postboks 7800, 5020 Bergen, Norway E-mail Borge.Hamre ift.uib.no E-mail Jakob.Stamnes ift.uib.no Abstract A review is provided of ultraviolet (UV) and visible radiative transfer in an atmosphere-sea-ice-ocean system...

References

Ambach W, and Blumthaler M (1993) Biological effectiveness of solar UV radiation in humans. Experientia 49 747 - 753 American Cancer Society (2008) URL _1x_Skin_Cancer.pdf.asp sitearea PRO, accessed on 7 Feb, 2008 Blumthaler M, and Ambach W (1991) Spectral measurements of global and diffuse solar ultraviolet-B radiant exposure and ozone variations. Photochem. Photobiol. 54 429 - 432 Caldwell MM (1971) Solar ultraviolet radiation and the growth and development of higher plants. In AC Giese...

UV Reflectivity

The radiation environment in urban areas depends, to a large extent, on the reflectivity of the building materials, paving surfaces, and vegetation. Reflectivities in the UV for many surfaces have been tabulated (Sliney, 1986 Blumthaler and Ambach, 1988 Feister and Grewe, 1995 Heisler and Grant, 2000a). However, reflectivity differences for particular materials within a type (i.e., variances in (1) color and kind of paint, (2) concretes, (3) building siding, and (4) specialty glass) seldomly...

Highlights of Other Collaborations

In addition to the UVMRP sponsored and funded research efforts described in Sections 8.7.1 through 8.7.6, further research collaborations include Cornell University Dr. Craig N. Austin has focused his research on how UV-B radiation affects the development of powdery mildew on the fruit and foliage of wine grape plants grown in the Finger Lakes Region of New York State. For two summers, the UVMRP supplied a portable UV-B monitoring instrument used in some components of the studies. The...

Action Spectra and Irradiance Trends

An action spectrum A(A) is a weighting function of wavelength A that estimates the relative strength of a process (e.g., biological process or material degradation) for each wavelength in a range from A1 to A2. The action spectrum is multiplied by the irradiance I(A, t) to obtain a production function PACT(t). A direct comparison of dose amounts for any causal effect is not given by A(A), but just indicates the relative effect of each wavelength. Frequently, what is wanted is the time...

Ecological Implications

The body of evidence to date indicates that changes in UV effects on plants are often relatively subtle, but these small changes may have important ecological implications, particularly by secondary or indirect effects (Caldwell et al., 2007). The small changes in leaf optical properties and secondary chemistry, and minimal differences in productivity under simulated global dimming and UV-B reduction found in our study, are consistent with this perspective. Changes in the quantity of UV...

Reduction of UV Irradiance by Clouds and Aerosols

A measured daily cycle of UV reaching the surface will show large UV irradiance reductions from clear-sky conditions as clouds pass over a site while blocking the view of the sun. These reductions are frequently in excess of those caused by measured ozone changes from climatological values for wavelengths longer than 305 nm. In general, the effect of clouds and aerosols reduces the UV and VIS amounts at all wavelengths reaching the earth's surface. When using satellite data to estimate the...

Air Pollution Gases and Aerosols

Wide varieties of pollutants are emitted to the atmosphere each year by the tons. The Environmental Protection Agency (EPA) has chosen to classify them in two broad categories based on their respective origination points. 1. Primary Pollutants are those classified as being emitted directly from sources and not undergoing any chemical or physical transformation. An example would be the carbon monoxide emitted through the automobile exhaust. Such gases are called non-reactive since they generally...

Tree and Building Influences on UV 12431 Measurements

Along with protective clothing and sunscreen use, seeking shade is a primary means recommended by public health agencies to avoid excess exposure to UV radiation (Environmental Protection Agency, 1995 Parisi and Kimlin, 1999 Saraiya et al., 2004). However, tree effects on UV may differ significantly depending on the view of the sky and to some extent, the trees species. Ultraviolet shadows generally differ substantially from the shadows of visible light (Heisler et al., 2003 a) with UV shadows...

Main Objectives

The main objective of this UV-B study was to examine the qualitative effects of UV radiation on the early development of soybean (Glycine max), using two varieties Williams and Forrest. The goals of the study were to (1) evaluate the initial responses to low dose UV radiation in newly emerging plants up to 28 days post-germination (2) evaluate effects of UV radiation on the seed production and viability of seed by examining the viability of the seeds produced from plants receiving a low dose UV...

Solar UV and PAR Irradiance

Measurements of ambient solar UV and PAR were made using a broadband UV 376 sensor (Skye UV-B Skye Instruments, Ltd., Powys, UK) and quantum sensor (LI-185, Li-COR, Inc., Lincoln, NE, USA), respectively, at the Mauna Kea field site during the experiments. Clear-day data during the experiment were regressed against biologically-weighted estimates calculated from solar UV irradiance measured at the USDA UV-B monitoring station UVMFRS radiometer located at the Mauna Loa Meteorological Observatory...

Leaf Optical Properties

Changes in leaf spectral reflectance, transmittance, and absorbance to UV visible light of pecan leaves throughout a growing season are illustrated in Fig. 18.3. The changes in leaf optical properties were relatively small in UV-B (280 nm - 320 nm) and UV-A (320 nm - 400 nm) spectral regions compared to that of the visible spectral region (400 nm - 760 nm). Throughout the growing season, pecan leaves reflected 4 - 8 , transmitted 0 -1 , and absorbed up to 96 of UV radiation (280 nm - 400 nm)....

Utah State University

Stephen Flint, and colleagues from Utah State University, combined numerous UV radiation related studies to determine and evaluate various UV-B and UV-A biological weighting functions. Weighted UV doses based on this and other work are routinely calculated and posted on the UVMRP website. Field experiments were conducted on Mauna Kea, HI at approximately 3000 m elevation to test the relative importance of the UV-B and UV-A wavebands under near ambient, no UV-B, and no UV-A or...

Crop Response to Drought

Climate change is predicted to bring regional-scale precipitation extremes, causing both flooding and drought in certain areas (Giorgi et al., 1998). Most model simulations predict decreased precipitation by the end of the 21st century in subtropical regions (IPCC, 2007). Increased precipitation extremes are also likely in major agricultural production areas, e.g., southern and eastern Asia, eastern Australia, and northern Europe (Christensen et al., 2007). The 2003 summer drought in Europe...

Ultraviolet Radiation and Its Interaction with Air Pollution

Wenny 1 North Carolina State University, Department of Marine, Earth, and Atmospheric Sciences, Campus Box 8208 Raleigh, North Carolina 27695-8208, USA E-mail SBarn46193 aol.com 2 MODIS Characterization Support Team (MCST) Sigma Space Corp. 10210 Greenbelt Road, Suite 500 Lanham, MD 20706 E-mail brian.wenny gmail.com Abstract This chapter contains the methodology, along with study examples, that show the types of interactions that the sun's ultraviolet (UV)...

Human Exposure to UV

From the viewpoint of human exposure to UV, the maximum clear-sky UV irradiance and exposure occurs in the equatorial zone latitudes, 23.3 ,following the seasonal sub-solar point, and at high mountain altitudes. In general, UV erythemal, UV-A, and UV-B irradiance decreases with increasing latitude outside of the equatorial zone, due to the decreases in maximum daily noon solar elevation angles and for UV-B increases in ozone amount. An exception occurs for UV-B wavelengths at southern mid- to...

Relationship Between UVyitD and UVEry

The relationship between UVVitD and UVEry, as deduced from several years of spectral UV data from Lauder, New Zealand, is shown in Fig. 2.12. At first impression, the plot in the upper panel seems to indicate a close proportionality between the two quantities, with UVVitD being approximately 2 x UVEry (for standard normalization). However, at lower values, which are characteristic of the situation throughout winter months, this proportionality breaks down. For the truncated version of the...

Radiation Amplification Factor

An alternate method for the estimation of long-term changes in UV-B irradiance can be devised by combining measured ozone values with radiative transfer calculations. These calculations can be simplified for estimating irradiance change by neglecting scattering effects. For clear-sky, constant cloud, and constant aerosol conditions, changes in monochromatic UV-B irradiance dF show a well-defined inverse relation with changes in the amount of ozone d in the atmosphere based on laboratory...

Light Interaction with Absorbing and Scattering Media

The absorption coefficient a(A), the scattering coefficient a(A), and the scattering phase functionp(A, 0), can be expressed as The subscript i is used to denote the various radiatively-active components, i.e., air molecules, aerosols, and liquid water and ice cloud particles in the atmosphere ice crystals and impurities in the snow brine pockets and air bubbles in the ice pure water mixed with air bubbles, chlorophyll, inorganic particles, and yellow substance in the ocean. Here A is the...

Crop Response to Atmospheric CO2 Concentration

The projected increase in atmospheric CO2 is expected to enhance growth and production of agricultural terrestrial plants (Easterling et al., 2007). Studies have also shown that the effects of elevated CO2 on plant growth and yield may depend on photosynthetic pathway, plant species, growth stage, and management practices, such as water and nitrogen applications (Jablonski et al., 2002 Kimball et al., 2002 Ainsworth and Long, 2005). Crops with C3 photosynthetic pathway respond markedly to...

Instrumentation

Instrumentation for measuring solar radiation reaching the ground falls into a few main classes, which have been described at length in specialized literature and reports. The earliest reliable device for quantitative measurements of solar radiation was a pyranometer (Kerr et al., 1967), which converted the sun's photon energy into heat and then into a voltage or current proportional to the energy-weighted integrated solar photon flux (Fig. 5.1(a)). Pyranometers are still deployed at many...

Crop Response to Multiple Abiotic Stress Factors

In natural habitats, plants are routinely subjected to a combination of abiotic factors. Under climate change scenarios, plants will be exposed to CO2, UV-B radiation, temperature, and water stress simultaneously and their performance can be assessed only when grown under these multiple abiotic stress conditions. Many recent studies suggest that temperature and precipitation changes in future decades will modify, and often limit, the direct effect of CO2 enrichment on plants (Easterling et al.,...

Global Dimming and UVB Potential Effects on Plants

Reductions in shortwave radiation with increased atmospheric aerosols and other particulates are well established. This reduction of total shortwave radiation also coincides with an increase in the diffuse portion of the shortwave radiation (Black et al., 2006 Roderick, 2006) as aerosols and particulates increase the scatter of direct beam radiation (Fig. 13.1). Surface ultraviolet radiation (UV < 400 nm) levels are also influenced by atmospheric aerosols and other pollutants, both causing...

Strategies for Protection against UVB Radiation

Plants have evolved through several mechanisms by which they protect themselves from the damaging effects of UV-B radiation (Table 14.3). Table 14.3 Protective mechanisms against damage by UV-B radiation in plants. Adapted with permission from Prasad et al. (2003b) DNA repair photo-reactivation enzymes (photolyase) excision repair by removing damaged part of DNA bypass damaged DNA and fill gaps later from sister duplex. Increase reflectance to avoid entry of UV-B radiation through cuticle wax,...

Radiative Transfer in a Coupled Atmosphere SnowIce Ocean Casio System

Solar irradiance levels play a key role for energy exchange and primary production in marine polar environments. Because the ocean is typically covered by sea ice and snow for several months of the year, theoretical and experimental knowledge of radiation levels at various depths in the snow, ice, and ocean is essential. The photosynthetically active radiation (PAR, 400 nm < A < 700 nm) drives the pelagic primary production in general, and the amount of PAR reaching the bottom of the sea...

Scattering

As one would guess, this denotes a change in the direction in which radiation propagates. Radiation is shifted out of one direction and into another. In general, there can be a shift in frequency upon scattering as well. The wavelength dependence of molecular scattering (i.e., Rayleigh scattering) is proportional to A 4, so this scattering will be more significant in the UV range than in the visible. The change in direction of radiation associated with scattering is described by the phase...

Impact of Solar UV on Human Health

The potential consequences of global climatic change (GCC) with regard to human health have recently been the subject of numerous reviews (e.g., Leaf, 1989 Longstreth, 1991 Epstein, 1998 Longstreth, 1999). For the most part, the possibility of increased negative effects could only occur when the incidence of disease is linked to the tropics or other warm weather regions. However, it is also clear that in most locations, GCC will only affect the risk of disease if the disease already exists at...

Specific Effects of UVB Radiation on Plants

Ultraviolet Leaf Plants

Plants are highly sensitive to UV-B radiation because of their sessile nature. In plants, UV-B radiation damages cell membranes and all organelles within the cell, including the chloroplasts, mitochondria, and deoxyribonucleic acid (DNA) within the nucleus. Damage to these cell organelles directly or indirectly affects basic plant metabolic processes, such as photosynthesis, respiration, growth, and reproduction. Consequently, UV-B damage harms crop yield and quality. An overview of various...

Spectrum of Solar Radiation

Figure 9.1 shows the incident UV, visible, and near-infrared parts of the spectral solar irradiance (wavelengths shorter than 1,000 nm) measured on board an earth-orbiting satellite (Rottman et al., 1993). Spectra of an ideal blackbody at several temperatures are also shown in Fig. 9.1. Given the requirement that the total solar energy emitted be the same as that emitted by a blackbody, one finds that the sun's effective temperature is 5,778 K. If the radiating layers of the sun had the same...

Introduction

The growing population of today's world (6.7 billion, U.S. Census Bureau, 2008) faces great challenges due to limited resources for the production of adequate amounts of food, fiber, feed, industrial products, and ecosystem services. As the global population increases by nearly 80 million each year, policies must be developed to ensure the needs of a future population of 8 billion by 2025 and more than 12 billion by 2050 (U.N. Population Division, 2008) are met. About 84 of this growth is...

Peak UV

For some biological processes, peak UV intensity may be more important than the mean value, and while we cannot be sure about evolutionary pressures, it is possible that UV intensities were much greater during the earlier history of the planet than at present (Bj rn and McKenzie, 2007). However, from our current perspective, changes in UV over the past, and future, few decades are more relevant. It is likely that peak UV over these time scales has already occurred, since it is expected that...

Dosimetry UV Modeling and Instruments

Every wavelength causes differing biological effects. Four Action Spectra for different biological targets are shown in Fig. 4.17. It is evident that UV-B is the main culprit for harmful UV consequences, in particular erythema. Convolving a solar UV irradiance spectrum with the specific action spectrum and then integrating Figure 4.17 Action spectra for several biological targets. Source Di Menno et al., 2007 Figure 4.17 Action spectra for several biological targets. Source Di Menno et al.,...

Data Collection and Processing

Two data loggers are installed at each site to collect and transfer the direct measurements from the instruments referred to in Table 8.1. One data logger is used to collect the data every 15 seconds from the VIS-MFRSR, UVB-1 pyranometer, temperature humidity sensors, and the downward looking LI-COR 210SA photometer. The other is for the UV-MFRSR, PAR Quantum sensor, and barometer (and UV-A radiometer where applicable) that are sampled every 20 seconds. The difference between the sampling...

Depth of Light Penetration into Leaf Tissues

Light attenuation in pecan leaves at four wavelengths including UV-B, UV-A, blue light, and red light into leaf tissues is illustrated in Fig. 18.5. The depths of the light penetration into the leaf tissues are presented in Fig. 18.6. Pecan leaf epidermis strongly attenuated 310 nm UV-B, 98 of which was absorbed within the first 10 m of the 15 m-thick upper epidermal tissue (Figs. 18.5 and 18.6). High UV-B attenuation by the epidermal layer means low epidermal transmittance to UV-B. Figure 18.4...

Crop Response to Temperature

The inferences from global circulation model simulations indicate that earth's mean surface air temperature warming for a doubling of atmospheric CO2 is expected to increase by 2 C - 4.5 C (IPCC, 2007). Additionally, it is projected that heat waves will be more intense, more frequent and longer lasting in future warmer climates (Meehl and Tebaldi, 2004). Daily minimum temperatures (nighttime temperature) are projected to increase faster than daily maximum temperature (daytime), leading to...

List of Contributors

11 1 2 Julia Lee-Taylor , Sasha Madronich , Christopher Fischer , and Bernhard Mayer National Center for Atmospheric Research, Boulder, Colorado, USA Deutsches Zentrum f r Luft- und Raumfahrt, Oberpfaffenhofen, Germany Richard L. McKenzie and J Ben Liley National Institute of Water and Atmospheric Research (NIWA), Lauder, Central Otago, New Zealand 9352 NIWA Lauder, Private Bag 50061 Omakau, Central Otago 9352, New Zealand E-mail r.mckenzie niwa.co.nz E-mail b.liley niwa.co.nz Germar Bernhard,...

Single Scatter Albedo

Absorption and scattering by particles can be simultaneously important, dependent upon the physical-chemical makeup of the particle. The measure of the relative importance of scattering to absorption is the single scatter albedo, S70, defined as For purely scattering particles, S70 1, and for purely absorbing particles, sj0 0. Neither extreme will be encountered in the ambient atmosphere where values generally range from 0.55 to 0.95. The single scatter albedo ( 0) is related to the amount of...

Climatology of UVA Irradiance

Figure 3.9 shows the climatology of UV-A irradiance (spectral irradiance integrated between 315 nm and 400 nm) for all UVSIMN sites but Summit. All plots show individual measurements, as well as the average, median, and 10th and 90th percentiles, and overall daily maximum. Since long-term changes in cloud cover and albedo are not considered in this study, historical estimates are virtually identical with recent measurements and are therefore not included in Fig. 3.9. Changes in total ozone have...

UV Exposure Regimes Greenhouse studies

The greenhouse UV-B treatment was based on the exposures found in the conterminous United States. Analysis of the probability of having four hours in a day with an upper 5 daily exposure of 8 kJ m UV-Bbe (based on the action spectrum of Caldwell, 1971) occurs approximately 5 of the days in June and July (Grant and Slusser, 2002). During the early part of June, the soybean crops are in early vegetative stages. A 3-day sequence of such exposure levels occurs approximately 1 of the time (Grant and...

UV Effects on Early Development and Survival of Young Soybean

Soybeans are generally planted close to the surface of soil however, little UV radiation is said to penetrate any soil type. Organisms are most prone to cell and genetic alteration during periods of rapid call division and growth, as would be the case for plants in the first 3 to 4 days after planting, when the seed is germinating. We have been intrigued by the reports that plants appear to be the most affected by UV radiation in the first 3 weeks of growth, particularly in terms of the leaf's...

Abiotic Stress Tolerance and Cultivar Screening Tools

There is a large variation in tolerance or susceptibility to abiotic stresses, particularly to different climate change factors including UV-B radiation (Reddy et al., 2005 Singh et al., 2008a), high temperature stress (Craufurd et al., 2003 Prasad et al., 2006b Ristic et al., 2008), and water stress (Foulkes et al., 2002 Upadhyaya, 2005 Bakheit, 2008 Singh, 2008). This variation can provide an opportunity for genetic improvement of plant species through either traditional plant breeding...

Estimating UV Trends Satellites

Global estimates of surface UV irradiance Fx as a function of latitude, longitude, and wavelength A have been calculated from satellite measurements of atmospheric backscattered UV radiances and the small amount reflected from the surface. The long-term precision and stability of a satellite instrument's in-flight calibration, especially the single-channel radiances used to estimate cloud transmission and reflectivity, make it very useful for estimating trends in F . In the absence of a widely...

Global Climatologies of UVEry and UVyitD

Global UV climatologies (Lee-Taylor and Madronich, 2007), which were calculated with the TUV1 radiative transfer model (Madronich and Flocke, 1995), were used to directly compare vitamin D weighted UV and erythemally weighted UV. In both cases, the weighting functions are as adopted by the CIE, extending to 400 nm in the case of UVEry, (McKinlay and Diffey, 1987), and to 330 nm in the case of UVVitD (Bouillon et al., 2006). If the truncated version of the vitamin D action spectrum had been...

Comparison of Radiation Levels at Network Sites

There are substantial differences in the UV climatology between the various UVSIMN sites. A large portion of the differences can be traced to their geographical locations as lower latitudes experience higher sun elevations and more UV, all other factors being equal. However, the contention that low levels of UV will occur in Polar Regions because of the high latitude is shown here to not be true. Measurements from the seven network sites are presented below. The comparison is based on the...

Results

1.3.1 Satellite-Derived UV Climatologies The geographical distributions of daily UV radiation doses at earth's surface, averaged over the entire time period of (Nov. 1, 1978 - June 30, 2000) are shown in Figs. 1.2 -1.6. The upper panel in each figure shows values calculated by considering the effects of both ozone and clouds, as estimated from TOMS data, and are thus assessed to be nearest to the actual values experienced over this time period. The lower panels show climatological distributions...

UV Index and Units

Erythemal irradiance is frequently expressed in terms of the UV index 25 mW per m2 2.5 W per cm2. The index is an arbitrary unit such that very high values reported by weather services have a UV index of 10 (25 W per cm ). Erythemal exposure or dose is a time-integrated quantity normally expressed in kJ per m2. Many high altitude locations with extreme UV amounts can exceed 10 on clear days. The weather service for the populated region near Cuzco, Peru, frequently reports a UV index of 10 to 11...

Estimates of Historical UV Indices

Based on historical ozone data and model calculation, the climatology of the UV Index for years preceding the development of the ozone hole was estimated for all sites with the exception of San Diego and Summit. The procedure is explained using South Pole as an example. Historical total ozone data at South Pole are available from observations of Dobson spectrophotometers performed by the Global Monitoring Division (GMD) of NOAA's Earth System Research Laboratory (ESRL) (Climate Monitoring and...

An Inconsistency

The above discussion points to an inconsistency between the CIE spectrum for vitamin D (Bouillon et al., 2006) and the statements made in the literature about our ability to photosynthesize vitamin D in summer and winter, namely that a few minutes daily exposure to sunlight in summer is sufficient at mid-latitudes (Holick, 2002 2007), and that no vitamin D is produced in Boston in winter (Webb et al., 1988). The first statement above is based on the supposition that 1 MED full body exposure...

Calculation of Optimal Times for Exposure to Sunlight

The optimal time for exposure to sunlight that is needed to receive adequate UV for vitamin D production, but without inducing erythema, depends strongly on latitude and season. Here we develop algorithms for calculating the time in terms of the widely used UVI. We can calculate the time taken (tE in minutes) to induce skin damage (one minimum erythemal dose) using where the factor 4000 60 accounts for the conversions from UVEry to UVI and seconds to minutes UVI is the UV Index ( 40 x UVEry,...

Uvmfrsr Data Processing

The UV-MFRSR uses independent interference filter-photodiode detectors and an automated rotating shadow band to measure the total horizontal and diffuse horizontal UV solar irradiance at seven wavelengths concurrently Michalsky et al., 1988 Harrison et al., 1994 . Direct normal irradiance is determined within the data logger by subtracting the diffuse from the total signal, followed by a correction for imperfect cosine response. The UV-MFRSR instruments provide synchronized measurements of...