Surface UV radiation monitoring based on GOME and SCIAMACHY

Jos van Geffen, Ronald van der A, Michiel van Weele, Marc Allaart and Henk Eskes
in: Proceedings of the ENVISAT & ERS Symposium, 6-10 September 2004,
Salzburg, Austria, ESA publication SP-572, 2005 (CD-ROM).

1. Introduction

Atmospheric ozone shields life at the Earth's surface from the most harmful components of the solar UV radiation. Thinning of the atmospheric ozone, e.g. due to ozone depletion and changes in the meteorology in the stratosphere, leads to elevated levels of UV-B radiation at the Earth's surface. A decrease in ozone of 1%, for example, will lead to an estimated increase in UV-B of about 2%. Exposure to enhanced UV incidence increases the risks of biological damage to humans, animals and other organisms. It is therefore important to monitor surface UV levels on a global scale and to do this over a prolonged period of time. Information on biological effects and their dependence on ozone column values can be found in, for example, Refs. [1,2] and references therein. Information on UV radiation for the general public can be found in Refs. [3,4].

Within the project Tropospheric Emission Monitoring Internet Service (TEMIS) a near-real time service has been set-up for total ozone and surface UV data. The satellite measurements of the near-real time ozone column by GOME (aboard the ERS-2 satellite) and SCIAMACHY (aboard the ENVISAT satellite) are assimilated in a transport model in order to produce near-real time global maps of ozone at local solar noon. This in turn is converted to global maps of the surface UV radiation for local solar noon and clear-sky conditions (UV Index). Further, the daily UV dose is computed for the last complete day using hourly cloud information from METEOSAT for Europe. Additionally, world-wide UV doses are calculated afterwards using cloud climatology data from ISCCP as soon as these are made available. Time series of UV index and UV dose for the GOME measurement period are completed and are continued using SCIAMACHY measurements. All data files and images are delivered via the TEMIS website at http://www.temis.nl/uvradiation/.

The paper first gives a brief introduction to UV radiation and introduces the action spectra of the effects of UV radiation used for the TEMIS service. Then the method used for determining the UV index and UV dose are outlined, which is followed by some examples of a preliminary validation. Next an overview is given of the data products of TEMIS, and finally some concluding remarks and suggestions for improvements are formulated.


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created: 3 September 2004
last modified: 1 September 2005