Description: Das Projekt "UV Climatology and Assessment of Long Term Trends" wird vom Umweltbundesamt gefördert und von Physikalisch-Meteorologisches Observatorium Davos und Weltstrahlungszentrum (PMOD,WRC) durchgeführt. Ultraviolet radiation reaching the earth' surface is highly varying, temperally and spatially. Moreover, the intensity depends very strongly on wavelength with a sharp decrease below about 300-310 nm by several orders of magnitude over a range of a few nanometers. The observed downward trend of the ozone in the stratosphere changes the UV reaching the surface on a longterm basis. Due to the high natural variability and the spectral behaviour it is very difficult to measure the UV radiation reaching the ground accurately and even more so, to determine trends. For the accurate measurement of UV radiation it is proposed to use sunphotometers with filters at 310, 320 and 340nm with a bandwidth of 1, 2 and 4nm respectively. These instruments have viewing angles of the order of 5 to 10 degrees, depending on their use as instruments to measure direct solar irradiance or sky radiance. The calibration is performed in close co-operation with the Physikalisch-Technische Bundesanstalt (PTB) in Berlin which has longstanding experience with this wavelength range and an accuracy of plus minus 0.5 Prozent is expected. From the measurement of the direct solar irradiance, the sky radiance in the almucantar at 10 degrees from the Sun and the radiance at two elevation angles in the vertical perpendicular to the Sun the 2 irrandiance on a horizonal surface (UV global radiation) can be calculated for the three wavelengths. The extrapolation to other wavelengths can be performed using atmospheric models for the calculation of the spectral radiance. From such spectral data the UV irradiance for any sensitivity curve (biological or instrumental) can be determined. It is expected that this method yields UV global radiation under clear sky conditions with an accuracy of by comparison with the data gathered by Bener in the sixties longer term trend might also be determined. The calibration of the Bener should be tracible as the standard lamps used are still available. The objective is the experimental determination and documentation of the anticipated long term trend of UV-B related to the depletion of stratospheric ozone. Measurements of direct solar irradiance and sky radiances (view angle of 20.) at four selected angles are performed during clear days with Precision UV-Filter Radiometers (PUV-FR) at 310, 320 and 340 nm. A cryogenic radiometer based calibration (cooperation with PTB, Berlin) guarantees an absolute accuracy of the PUV-FR. Leading Questions: How large is the expected trend in the UV global radiation and how is it related to the changes in stratospheric and tropospheric ozone content? What is the absolute accuracy whith which these trends can be determined? What is the relevance of trends compared to natural variability?
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Ozon ? Ozonwert ? Berlin ? Davos ? Biopharmazeutikum ? Tieftemperaturtechnik ? Globalstrahlung ? Kalibrierung ? Klimatologie ? Solarstrahlung ? UV-Strahlung ? Bodennahes Ozon ? Radiometrie ? Strahlungsmessung ? Zeitreihenanalyse ? Strahlung ? Globale Erwärmung ? Filter ? Gewährleistung ? Altlampe ? Hochrechnung ? Atmosphärenmodell ? Beleuchtungsstärke ? Stratosphäre ? Daten ? Abbau der Ozonschicht ? Spektrum ? Globale Aspekte ? Erdoberfläche ? Zeitverlauf ? solar spectal irradiance ? ultra violet ? variability of UV radiation ? Messgenauigkeit ? ozon layer ?
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 1993-01-01 - 1997-06-30
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