Effects of clouds on erythemal and total irradiance as derived from data of the Argentine Network

Cede, Alexander; Blumthaler, M.; Luccini, Eduardo; Piacentini, R. D.; Núñez, Liliana

doi:10.1029/2002gl015708

Cited by 46 publications

(39 citation statements)

References 13 publications

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“…Those circulation anomalies then drive variability in cloud cover and thus variability in UV radiation reaching the boundary layer, which in turn is seen in phase-to-phase variability in surface ozone concentrations in Mexico City. The cloud-UV radiation portion of our hypothesis is supported by Kerr and Fioletov (2008), who found that typical UV transmission ratios range between 0.3 and 0.8 for overcast conditions (Cede et al, 2002) and as little as 0.05 for thick cumulonimbus clouds (McArthur et al, 1999). It is also supported by An et al (2008), who found a strong relationship between surface ozone concentrations in Beijing and surface UV radiation, particularly in summer, and noted that surface UV was up to 200 % more sensitive to total cloud cover than was surface total radiation.…”

Section: Introductionsupporting

confidence: 72%

Variability of winter and summer surface ozone in Mexico City on the intraseasonal timescale

Barrett

Raga

2016

Atmos. Chem. Phys.

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Abstract. Surface ozone concentrations in Mexico City frequently exceed the Mexican standard and have proven difficult to forecast due to changes in meteorological conditions at its tropical location. The Madden-Julian Oscillation (MJO) is largely responsible for intraseasonal variability in the tropics. Circulation patterns in the lower and upper troposphere and precipitation are associated with the oscillation as it progresses eastward around the planet. It is typically described by phases (labeled 1 through 8), which correspond to the broad longitudinal location of the active component of the oscillation with enhanced precipitation. In this study we evaluate the intraseasonal variability of winter and summer surface ozone concentrations in Mexico City, which was investigated over the period 1986-2014 to determine if there is a modulation by the MJO that would aid in the forecast of high-pollution episodes.Over 1 000 000 hourly observations of surface ozone from five stations around the metropolitan area were standardized and then binned by active phase of the MJO, with phase determined using the real-time multivariate MJO index. Highest winter ozone concentrations were found in Mexico City on days when the MJO was active and in phase 2 (over the Indian Ocean), and highest summer ozone concentrations were found on days when the MJO was active and in phase 6 (over the western Pacific Ocean). Lowest winter ozone concentrations were found during active MJO phase 8 (over the eastern Pacific Ocean), and lowest summer ozone concentrations were found during active MJO phase 1 (over the Atlantic Ocean). Anomalies of reanalysis-based cloud cover and UV-B radiation supported the observed variability in surface ozone in both summer and winter: MJO phases with highest ozone concentration had largest positive UV-B radiation anomalies and lowest cloud-cover fraction, while phases with lowest ozone concentration had largest negative UV-B radiation anomalies and highest cloud-cover fraction. Furthermore, geopotential height anomalies at 250 hPa favoring reduced cloudiness, and thus elevated surface ozone, were found in both seasons during MJO phases with abovenormal ozone concentrations. Similar height anomalies at 250 hPa favoring enhanced cloudiness, and thus reduced surface ozone, were found in both seasons during MJO phases with below-normal ozone concentrations. These anomalies confirm a physical pathway for MJO modulation of surface ozone via modulation of the upper troposphere.

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Section: Introductionsupporting

confidence: 72%

Variability of winter and summer surface ozone in Mexico City on the intraseasonal timescale

Barrett

Raga

2016

Atmos. Chem. Phys.

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“…Thus, the total global solar radiation is usually more attenuated by clouds than erythemal UV. This is caused by the much higher contribution from the direct component for total global radiation than for erythemal radiation [48]. One additional reason for the different effects of clouds on erythemal and total global solar radiation is the fact that water does not absorb in the UV, but it has strong absorption bands mainly in the infrared band [48].…”

Section: Cloudsmentioning

confidence: 98%

“…Enhancements up to 25% in the UV region have been reported by many investigators [43,49]. Enhancement episodes can last for hours [48]. Pfister et al [50] analysed one year of total global irradiance measurements at Lauder, New Zealand, and found that measured radiation enhancements of more than 10% appeared with a frequency of 5%.…”

Section: Cloudsmentioning

confidence: 99%

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Solar radiation and human health

Moan

Juzeniene

2010

Journal of Photochemistry and Photobiology B: Biology

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The Sun has played a major role in the development of life on Earth. In Western culture, people are warned against Sun exposure because of its adverse effects: erythema, photoimmunosuppression, photoageing, photocarcinogenesis, cataracts and photokeratitis. However, Sun exposure is also beneficial, since moderate doses give beneficial physiological effects: vitamin D synthesis, reduction of blood pressure and mental health. Shortage of Sun exposure may be even more dangerous to human health than excessive exposure. Avoiding Sun exposure leads to vitamin D deficiency which is associated not only with rickets and osteomalacia, but also with increased risk of cardiovascular disease, multiple sclerosis, rheumatoid arthritis, diabetes, influenza, many types of cancer and adverse pregnancy outcomes. Solar radiation induces nitric oxide release in tissue and immediate pigment darkening which certainly play important roles, although these are still unknown. Action spectra relevant for health are described. We will also review what is known about spectral and intensity variations of terrestrial solar radiation as well as its penetration through the atmosphere and into human skin and tissue.

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“…Thus, these enhancements can reach values of up to 30% over clear-sky values during several minutes in a row, pointing out the importance of these events [4,5] . The enhancements were found to be most pronounced for large cloud cover of 5 to 7 oktas when the solar disk is unclouded [6], being smaller in the UV band than in the visible and infrared intervals [7]. It is well documented that these short-term enhancements in UV levels may affect the photosynthesis rate of vegetation like marine algae or phytoplankton [8].…”

Section: Introductionmentioning

confidence: 96%

Study of UV cloud modification factors in Southern Patagonia

Wolfram¹,

Orte²,

Salvador³

et al. 2017

AIP Conference Proceedings

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How large and how long are UV and total radiation enhancements? AIP Conference Proceedings 1810, 110002 (2017) ewolfram@gmail.comAbstract. Anthropogenic perturbation of the ozone layer has induced change in the amount of UV radiation that reaches the Earth's surface, mainly through the Antarctic ozone hole, making the ozone and ultraviolet (UV) radiation two important issues in the study of Earth atmosphere in the scientific community. Also the clouds have been identified as the main modulator of UV amount in short time scales and produce the main source of uncertainty in the projection of surface UV level as consequence of projected ozone recovery. While clouds can decrease direct radiation, they can produce an increase in the diffuse component, and as consequence the surface UV radiation may be higher than an equivalent clear sky scenario for several minutes. In particular this situation can be important when low ozone column and partially cloud cover skies happen simultaneously. These situations happen frequently in southern Patagonia, where the CEILAP Lidar Division has established the Atmospheric Observatory of Southern Patagonia, an atmospheric remote sensing site near the city of Río Gallegos (51º55'S, 69º14'W). In this paper, the impact of clouds over the UV radiation is investigated by the use of ground based measurements from the passive remote sensing instruments operating at this site, mainly of broad and moderate narrow band filter radiometers. We analyzed the UV Index obtained from a multiband filter radiometer GUV-541 (UVI) [Biospherical Inc.] installed in the Observatorio Atmosférico de la Patagonia Austral, Río Gallegos, since 2005. Cloud modification factors (CMF, ratio between the measured UV radiation in a cloudy sky and the simulated radiation under cloud-free conditions) are evaluated for the study site. The database used in this work covers the period 2005-2012 for spring and summer seasons, when the ozone hole can affect these subpolar regions. CMF higher than 1 are found during spring and summer time, when lower total ozone columns, higher solar elevations and high cloud cover occur simultaneously, producing extreme erythemal irradiance at ground surface. Enhancements as high as 25% were registered. The maximum duration of the enhancement was around 30 minute. This produces dangerous sunbathing situations for the Río Gallegos citizen..

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Effects of clouds on erythemal and total irradiance as derived from data of the Argentine Network

Cited by 46 publications

References 13 publications

Variability of winter and summer surface ozone in Mexico City on the intraseasonal timescale

Variability of winter and summer surface ozone in Mexico City on the intraseasonal timescale

Solar radiation and human health

Study of UV cloud modification factors in Southern Patagonia

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