Seasonal variation of UV irradiation
UV irradiation depends on the month and on latitude. The UV irradiation received in summer (defined as June and July) is 5.1 (range: 2.4-11.3) times higher on average than in winter (defined as December and January).
Geographical distribution of UV irradiation
The geographical distribution of UV irradiance does not systematically follow a strong latitude gradient, particularly for late spring and early summer. For example:
- In France, the UV irradiation was higher in the south-east than in the south-west at the same latitude.
- The British Isles received a lower UV irradiation compared to similar latitude for the rest of Europe.
- The northern coast of Spain (northern to Cantabrian mountains) received less UV than the rest of the country.
- Nordic countries (Norway, Sweden and Finland) tend to receive higher UV irradiation than Germany or France in late spring and early summer.
Clusters of high UV irradiance can be identified within countries such as the Paris area in France.
The UV irradiation was correlated with the latitude for most of the months with higher UV irradiance for southern latitude. This correlation was stronger from October to February with 89% to 96% of the variance of the UV irradiation associated with the latitude. The association was lower for the sunniest months, with only 3% of the variance of the UV irradiation associated with the latitude in May.