General Characteristics

The climate of the Canary Islands, to the North of the Tropic of Cancer, is basically modulated by  the Azores high. The climatic characteristics of the Izaña Observatory (IZO) are driven by the altitude factor. IZO is located at 2400 meters above sea level above the quasi-permanent temperature inversion layer associated to the trade winds regime. The inversion layer separates the moist marine boundary layer from the dry free troposphere.  It can be  frequently well identified by the "sea of stratocumulus" can be seen on the northern coasts of the islands.

The climate at IZO is extremely dry most of the year.  Clean air from middle free troposphere gives to IZO a major scientific interest.  The insolation is very high, especially  in summer, recording the highest average annual insolation duration of Spain with 3448.5 hours/year. In winter nights there is a substantial thermal cooling, producing a large diurnal thermal oscillation.

Another important climatological factor is the proximity of the Canary Islands to the African continent. African Dust Intrusions occur during a significant number of days, mainly in summer time, producing a notable reduction in  horizontal visibility.

Climatology of the Izaña Observatory (IZO)

Frecuency of days of precipitation at IZO in the 1971-2000 period

The main precipitation is recorded in winter time when Atlantic lows pass over the Canary Islands.  In winter the thermal inversion layer is weak. Some days it even disappears or is found above the IZO altitude resulting in fog and  spectacular hoarfrost events. Strong winds and thunderstorms are also frequent , and the snow is present some days in winter.  The figure above presents the seasonal frequency of days of precipitation observed at IZO in the period 1971-2000. The annual average during this period is about 44 precipitation days.  From these,  in about 11 days  is recorded snow precipitation,  mainly from November to April and less frequently from May to October.