Long-term solar UV radiation reconstructed by Artificial Neural Networks (ANN)

International audienceArtificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980?1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions

Temperature dependence of the Brewer global UV measurements

Spectral measurements of global UV irradiance recorded by Brewer spectrophotometers can be significantly affected by instrument-specific optical and mechanical features. Thus, proper corrections are needed in order to reduce the associated uncertainties to within acceptable levels. The present study aims to contribute to the reduction of uncertainties originating from changes in the Brewer internal temperature, which affect the performance of the optical and electronic parts, and subsequently the response of the instrument. Until now, measurements of the irradiance from various types of lamps at different temperatures have been used to characterize the instruments' temperature dependence. The use of 50 W lamps was found to induce errors in the characterization due to changes in the transmissivity of the Teflon diffuser as it warms up by the heat of the lamp. In contrast, the use of 200 or 1000 W lamps is considered more appropriate because they are positioned at longer distances from the diffuser so that warming is negligible. Temperature gradients inside the instrument can cause mechanical stresses which can affect the instrument's optical characteristics. Therefore, during the temperature-dependence characterization procedure warming or cooling must be slow enough to minimize these effects. In this study, results of the temperature characterization of eight different Brewer spectrophotometers operating in Greece, Finland, Germany and Spain are presented. It was found that the instruments' response changes differently in different temperature regions due to different responses of the diffusers' transmittance. The temperature correction factors derived for the Brewer spectrophotometers operating at Thessaloniki, Greece, and Sodankylä, Finland, were evaluated and were found to remove the temperature dependence of the instruments' sensitivity.This article is based upon work from COST Action ES1207 “A European Brewer Network (EUBREWNET)”, supported by COST (European Cooperation in Science and Technology) and from the ENV59-ATMOZ (“Traceability for atmospheric total column ozone”) Joint Research Programme (JRP)

Vertical distributions of ozone in the lower stratosphere over Antarctica and their relations to the spring depletion

Abstract - Three year observations of vertical ozone distributions (1985 - 1987) are analyzed, which have been gained by means of electrochemical ozone sondes (OSE-3) at GEORG FORSTER station (71°S; 12°E). This material and additional data of other stations are used to discuss the primary chemical origin of the spring time ozone depletion in connection with dynamically conditioned variations of ozone distribution in the southern polar stratosphere. A mean pattern featured by three typical time periods of the ozone depletion using the height-time variations of pronounced maxima of the vertical ozone distribution is drawn to localize the chemical active regionDuring spring in 1987 the ozone variations are discussed in more detail to separate different dynamical impacts like an irregular outflow of ozone into the troposphere and the control of vertical ozone distribution by dynamics of the southern polar stratospheric vortex itself. The special dynamical preconditions rendered it possible to use the height variations of stratospheric ozone as an indicator for the verticl diabatic circulation inside the polar stratospheric vortex

Evidence of a possible turning point in solar UV-B over Canada, Europe and Japan

This study examines the long-term variability of UV solar irradiances at 305 nm and 325 nm over selected sites in Canada, Europe and Japan. Site selection was restricted to the availability of the most complete UV spectroradiometric datasets during the period 1990-2011. The analysis includes the long-term variability of total ozone, aerosol optical depth and cloud fraction at the sites studied. The results, based on observations and modeling, suggest that over Canada, Europe and Japan the period under study can be divided into three sub-periods of scientific merit: the first period (1991-1994) is the period perturbed by the Pinatubo volcanic eruption, during which excess volcanic aerosol has enhanced the "conventional" amplification factor of UV-B at ground level by an additional factor that depends on solar elevation. The increase of the UV-B amplification factor is the result of enhanced scattering processes caused by the injection of huge amounts of volcanic aerosols during the perturbed period. The second period (1995-2006) is characterized by a 0.14% yr -1 increase in total ozone and an increasing trend in spectral irradiance by 0.94% yr -1 at 305 nm and 0.88% yr -1 at 325 nm. That paradox was caused by the significant decline of the aerosol optical depth by more than 1% yr -1 (the "brightening" effect) and the absence of any statistically significant trend in the cloud fraction. The third period (2007-2011) shows statistically significant evidence of a slowdown or even a turning point in the previously reported upward UV-B trends over Canada, Europe and Japan. © 2012 Author(s)

Bewertung, Korrektur und komplexe Analyse einschliesslich Trenduntersuchung der langjaehrigen Ozonmessungen im Mitteldeutschen Raum Schlussbericht

Total ozone measurements at Potsdam and ozonesonde measurements at Lindenberg are homogenized and climatologically analyzed. Additionally to common procedures applied in homogeneity studies regression equations are used with aerological temperatures as predictors. These regression equations can and were used as quality checks for Dobson measurements as well as for prognostic purposes. Pattern of total column ozone as well as longterm ozone changes are shown to be weather pattern (WP) dependent, if an objective classification scheme for WPs is applied. This scheme uses information of the surface pressure and of the 500/1000 hPa thickness fields. The relations between the objectively classified WPs and the widely used ones of Hess-Brezowsky are discussed. In general, all WPs cause ozone decreases in the geographic area studied (40 -60 N, 10 W-20 E). Hence, changes of the atmospheric circulation modify the degree of zone decrease only, but do not result in a trend reversion. (orig.)Die Dobsonmessungen der Station Potsdam und der Ozonsondenmessungen von Lindenberg werden homogenisiert und klimatologisch ausgewertet. Zur Homogenisierung der Dobsonmessungen werden dabei neben den allgemein ueblichen Verfahren Regressionsbeziehungen mit aerologischen Temperaturwerten als Prediktoren verwendet, die sowohl als Qualitaetstest fuer die Dobsonmessungen als auch als Prognosegleichungen zur Vorhersage des Gesamtozongehalts verwendet werden koennen und wurden. Es wird gezeigt, dass sowohl die Verteilungsmuster des Gesamtozongehalts als auch die der langzeitigen Ozonaenderungen wetterlagenabhaengig sind, wenn zur Wetterlagenklassifikation ein objektives Klassifikationsschema mittels Clusteranalyse auf der Basis des Bodendruckfeldes und des Hoehendruckfeldes der 500 hPa-Flaeche verwendet wird. Diskutiert werden die Beziehungen zwischen objektiv klassifizierten Wetterlagen und den weit verbreiteten Wetterlagen nach Hess-Brezowsky. Fuer alle Wetterlagen wird fuer das Untersuchungsgebiet i.a. Ozonabnahme fuer alle Jahreszeiten gefunden. Aenderungen in der atmosphaerischen Zirkulation modifizieren damit auch die Staerken der Ozonabnahme, koennen aber eine Umkehr des Trends nicht bewirken. (orig.)Available from TIB Hannover: F96B1828+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

Survival of microorganisms under the extreme conditions of the Atacama Desert

Spores of Bacillus subtilis, conidia of Aspergillus niger, versicolor and ochraceus and cells of Deinococcus radiodurans have been exposed in the dark at two locations (at about 23 degrees S and 24 degrees S) in the Atacama Desert for up to 15 months. B. subtilis spores (survival approximately 15%) and A. niger conidia (survival approximately 30%) outlived the other species. The survival of the conidia and spores species was only slightly poorer than that of the corresponding laboratory controls. However, the Deinococcus radiodurans cells did not survive the desert exposure, because they are readily inactivated at relative humidities between 40 and 80% which typically occur during desert nights. Cellular monolayers of the dry spores and conidia have in addition been exposed to the full sun light for up to several hours. The solar fluences causing 63% loss in viability (F37-values) have been determined. These F37-values are compared with those determined at other global locations such as Punta Arenas (53 degrees S), Key Largo (25 degrees N) or Mainz (50 degrees N) during the same season. The solar UVB radiation kills even the most resistant microorganisms within a few hours due to DNA damages. The data are also discussed with respect to possible similarities between the climatic conditions of the recent Atacama Desert and the deserts of early Mars