Weather and climate in middle and high latitudes
The influence of maritime air masses can extend deep into Europe because there are few major topographic barriers to airflow and owing to the presence of the Mediterranean Sea. Hence the change to a more continental climatic regime is relatively gradual except in Scandinavia, where the mountain spine produces a sharp contrast between western Norway and Sweden. There are numerous indices expressing this continentality, but most are based on the annual range of temperature (see Note 1). Gorczynski’s continentality index (K) is:
A K = 1.7 ––––– –20.4
where A is the annual temperature range (°C) and ϕ is the latitude angle. (The index assumes that the annual range in solar radiation increases with latitude, but in fact the range is a maximum around 55°N.) K is scaled from 0 at extreme oceanic stations to 100 at extreme continental stations, but values occasionally fall outside of
these limits. Some values in Europe are London 10, Berlin 21, and Moscow 42. Figure 10.2 shows the variation of this index over Europe.