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Climatology

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

 

Month
Jan
Feb
Mar 
Apr
May
Jun
Jul
Aug
Sep
Oct Nov
Dec
Averag.Rain
3.12.12.32.41.80.60.40.92.85.25.55.4
Averag.Snow
3.1
2.1 2.1
0.8
0.1
0.0
0.0
0.0
0.0
0.1
0.6
2.4

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.

Statistics of monthly precipitation at IZO in the 1971-2000 period


Month
Jan Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Average
86.6
64.3
65.0
25.6
13.7
0.5
0.4
2.4
14.8
36.0
50.0
73.4
Minimum
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
Perc. 20
15.7
1.9
8.5
1.8
0.0
0.0
0.0
0.0
0.0
2.0
4.1
15.7
Perc. 40
31.6
18.3
25.8
9.3
0.1
0.0
0.0
0.0
3.4
7.8
22.9
39.2
Perc. 60
50.2
51.0
52.8
21.3
 5.30.0
0.0
0.0
13.4
31.1
37.5
60.9
Perc. 80
94.9
109.8
101.0
36.2
16.9
0.5
0.0
2.7
25.6
62.7
88.6
148.1
Maximum
957.4
342.4
354.9
185.0
213.4
6.5
8.4
24.4
65.9
211.7
193.1
241.6

The figure above presents the statistics of monthly precipitation for the period 1971-2000. The annual average for this period is 457.4 mm. The interannual variability is very high and some extreme rainfall events, have been observed (i.e.  957.4 mm in January 1979).

IZO's Climogram in the 1971-2000 period


Month
Jan
Feb
MarApr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Average
3.99
4.79
5.68
6.96
9.75
13.87
17.99
17.95
14.16
10.32
7.45
5.04
Max. Temp
7.19
8.16
9.31
11.05
14.08
18.39
22.53
22.38
18.24
13.92
10.71
8.16
Min. Temp
0.79
1.40
2.02
2.86
5.43
9.36
13.45
13.51
10.07
6.71
4.20
1.93
Precipitation
86.58
64.30
64.97
25.65
13.73
0.51
0.36
2.35
14.76
36.03
49.95
73.37

The precipitation is concentrated in six months from October to March, with an absolute maximum in December and January, and a secondary maximum in March. From April to September the precipitation is neglegible. Maxima temperatures are observed in July and August, and minima in January.


Statistics of maximum daily temperature at IZO in the 1971-2000 period


Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Average
7.15
8.15
9.30
10.99
14.03
18.34
22.48
22.36
18.20
13.88
10.69
8.13
Minimum
-2.0
-3.0
-2.8
-1.6
-2.0
5.8
8.4
11.8
3.6
1.8
-2.0-3.0
Perc. 20
3.4
4.4
5.16
7.211.0
15.6
19.5
19.6
15.0
11.0
7.6
4.5
Perc. 40
6.47.4
8.8
10.6
13.64
17.421.8
21.8
17.5
13.6
10.2
7.4
Perc. 60
8.6
9.8
11.0
12.6
15.2
19
23.8
23.64
19.5
15.2
12.0 
9.4
Perc. 80
10.8
12.04
13.4
15.0
17.0
21.28
25.8
25.4
21.8
17.0
13.8
12.0
Maximum
18.0
19.9
19.6
22.0
24.8
26.2
30.4
29.6
27.0
23.0
20.8
18.5

The 20th and 80th percentiles of daily maxima temperatures observed in the coldest months are 4 ºC and 12 ºC, respectively, whilst the minimum and maximum of daily maximum temperatures are -3 ºC  and 20 ºC, respectively.  During the hottest months the 20th and 80th percentiles are 20 ºC and 26 ºC, respectively with extremes of 8 ºC and 30 ºC. These maximum temperatures of 30 º C during the summer months are very high for a high mountain station.

Statistics of minimun daily temperature at IZO in the 1971-2000 period


Month
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Average
0.78
1.41
2.00
2.84
5.37
9.31
13.45
13.64
10.07
6.79
4.21
1.99
Minimum
-6.80
-9.80
-7.20
-5.40
-4.40
0.40
-0.20
3.20
1.00
-1.80
-4.00
-6.00
Perc. 20
-2.00
-1.80
-1.60
-1.00
2.00
6.88
10.20
10.50
7.00
4.00
1.36
-1.02
Perc. 40
-0.40
0.40
1.00
1.80
4.80
8.68
12.16
12.96
9.40
6.16
3.80
0.80
Perc. 60
1.80
2.60
3.00
4.00
6.80
10.00
15.00
15.00
11.00
7.80
5.20
2.80
Perc. 80
3.62
4.80
5.20
6.20
8.54
12.00
17.00
16.60
13.00
9.40
6.80
5.00
Maximum
10.10
11.00
11.00
13.40
15.40
17.60
20.80
19.80
18.80
16.20
12.80
11.40

The 20th and 80th percentiles of daily minimum temperatures observed in the coldest months are -2 ºC and 5 ºC, respectively, whilst the minimum and maximum of daily minimum temperatures are ‑10 ºC  and 11 º C, respectively.  During the hottest months the 20th and 80th percentiles are 10 ºC and 17 º C, respectively with extremes of 0 º C and 21 º C. Night frost is possible for most of the year (from October to May) and more probable in December and January.

Annual Wind Rose at IZO in the 1971-2000 period


The typical atmospheric circulation is the result of the surface anticyclone and high level ridge system, with NE flow at low levels (trade winds) turning counter-clockwise until becoming NW flow at the altitude of  IZO. Aside from this principal circulation, two other contributing flows may appear: The Western flow (mainly SW) tassociated to Atlantic perturbations and the S flow (SE in winter and SW in summer) associated to African dust Intrusions.

Evolution of the average annual temperatureat IZO in the 1915-2008 period

Evolution of the average annual precipitation at IZO in the 1915-2008 period
 


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