Abstract

UV-budget maps (the geographical distribution of effective UV at ground level) can be derived from satellite data. These UV-budget maps visualise changes in effective UV caused by ozone depletion and changes in cloud cover and aerosol content. Alterations in UV-budget maps over time give - in combination with dose-effect models for UV-induced effects - insight in the associated risks for human health and the environment. This report describes the results of the RUBEO-project: calculating Risks and Ultraviolet Budgets using Earth Observation (RUBEO). RUBEO aims at a better cloud parameterisation and incorporating temporal and spatial resolution for surface albedo, aerosol content and tropospheric ozone content. The geographical distribution of ozone and UV climatology and trends over Europe are analysed, and a cost-benefit analysis of satellite based UV budget mapping is provided. The UV-budget mapping can be applied using TOMS and GOME ozone data. A large scale statistical analysis of cloud effects is given comparing ISCCP and TOMS based remote sensing methods with cloud effects derived from ground measurements. Both satellite derived methods correlate well (r˜0.93) with the ground based analysis. Correction for non-zero albedo, under clear sky conditions, adds maximal 8% to the yearly effective UV-budget. Temporal and spatial differences in aerosol optical thickness and tropospheric ozone content, result in a decrease in effective UV of 3% for every 0.1 increase in aerosol optical thickness, and in a decrease in effective UV of 4% for every 10 DU increase in tropospheric ozone. Stratospheric ozone trends of -1 to -4% per decade observed over Europe correspond to a 0.5 to 4% increase in skin cancer weighted effective UV. The largest trends are seen in the central part of Western Europe.
At present satellite based UV-budget maps form a functional basis for trend analysis and risk assessment. However, satellite data and ground-based observations are both indispensable. Maps for changing UV-budgets and associated skin cancer risks have been used in 'state of the environment', reports. Such overviews, regularly published by the Dutch National Institute of Public Health and the Environment (RIVM) and the European Environmental Agency (EPA), support the evaluation and formulation of adequate environmental policies.

This report describes a project carried out in the framework of the Users Support Programme (USP-2), under responsibility of the Netherlands Remote Sensing Board (BCRS).