Annual variation in the ozone AOT40 value (May-July), 1996-2006
A number of stations were excluded from the analyses because data coverage was too low and/or the stations were not operational during at least 8 years in the period 1996-2006. Most stations are located in north-western Europe (Austria, Belgium, Germany, Switzerland, The Netherlands and the United Kingdom). Since a relative small number is located around the Mediterranean Sea, the selected stations are not representative for the whole of Europe. However, whilst the relatively short time series together with meteorological fluctuations add to the difficulty in drawing clear conclusions on trends, the area where the target value is exceeded appears to increase since 1998.