In Europe (EU25) about half a million skin cancer cases are occurring per year and this is strongly associated with personal habits in relation to sun exposure and its UV component. Within the frame of the European GMES-Program (GMES=Global Monitoring for Environment and Security) the ESA-GSE Project PROMOTE addresses this problem by developing and implementing a UV information service that aims to reach as many as possible citizens of Europe (EU25). The overall PROMOTE UV service contains forecast and monitoring products. The underlying methods, the use of satellite data, the various UV products including related user interfaces, as well as accuracy aspects are described. One central ambition of the PROMOTE project is the close interaction between providers and users. Experiences that have been made and will be made during the different stages of the PROMOTE project contribute significantly to the further up-grading of the services.
An efficient method for calculating and mapping surface UV radiation by use of satellite data and based on the independent pixel approximation has been developed. The method principally allows to take into account the total ozone column amount, the cloud optical depth, the surface elevation and albedo (snow, no snow) and the solar zenith angle. It is currently used for creating a UV climatology to study the effects of UV daily doses on marine ecosystems around the Norwegian Lofoten Islands. This study focuses on the temporal sampling of the cloud field and its effects on the calculation of UV daily doses. Three-dimensional radiative transfer calculations have been performed to estimate how many satellite overpasses or slots are needed to derive daily UV doses within certain limits of error. Shown are results for a synthetic cloud field having a pronounced asymmetry in cloud cover around noon time. For this case the daily dose can be derived with an error of 10% if the cloud field is at minimum probed every 60 minutes within the time interval from 10:00 to 14:00 assuming a constant cloud cover from sunrise to 10:00 and from 14:00 to sunset. Such a time sampling may be obtained from Meteosat data or from a combination of Meteosat and NOAA/AVHRR data. By using only NOAA/AVHRR data with a temporal resolution of typically 100 minutes at least 3 overpasses are needed to obtain the 10% relative difference between the derived daily dose and the exact reference value.
For the present investigation a new method for the calculation of the single scattering and absorption properties of hexagonal ice crystals called the Discretized Mie Formalism (DMF) is used together with a radiative transfer model in order to determine the influence of particle size and shape on the brightness temperature difference (BTD) between the two NOAA AVHRR infrared window channels 4 and 5. Comparing the results to those of optically equivalent spheres it is shown that particle shape has an influence on the observed BTD which is decreasing with increasing particle size.
Based on radiative transfer calculations it is studied whether Polar Stratospheric Clouds (PSCs) can be detected by the new Global Ozone Monitoring Experiment onboard the second European Research Satellite (ERS-2) planned to be launched in winter 1994/95. It is proposed to identify PSC covered areas by use of an indicator, the Normalized Radiance Difference (NRD), which relates the difference of two spectral radiances at 0.515 micrometers and 0.67 micrometers to one radiance measured in the center of the oxygen A-band at 0.76 micrometers . In presence of PSCs and under conditions of increasing solar zenith angles above O equals 80 degree(s) the NRD rapidly decrease to values clearly below those derived under conditions of a cloud free stratosphere. Calculations for O equals 86 degree(s) show that this method is successful independently from existing tropospheric clouds and by different tropospheric aerosol loadings or surface albedos. For solar zenith angles O < 80 degree(s) the PSC detection needs additional information about tropospheric clouds.
A bispectral approach for temperature determination of semitransparent clouds is applied to identify areas covered by Polar Stratospheric Clouds (PSCs). The method is based upon the information obtained from two satellite pixels and two spectral channels of the passive HIRS instrument onboard the NOAA satellites. Since PSCs form and emit in very cold stratospheric environments (< 195 K) solutions of the bispectral method yield low temperatures in a range that clearly differs from those derived for a cold but cloudfree stratosphere. Application of the method to NOAA satellite data gained during the major PSC event on January 31, 1989 demonstrates that large areas covered by dense PSCs are found with a horizontal distribution in very good agreement to independent airborne and satellite measurements.
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