Logo Centenario Izaña

The Izaña Observatory centenary: the exciting story of a mountain observatory on a remote island

By Fernando de Ory, PhD.


The Canary Islands were colonised over the 14th and 15th centuries, and in the year 1492 were already considered a strategic point on the sea route to the West Indies. Tenerife, the largest of the islands making up the Canary archipelago, has been of enormous scientific interest for centuries and, particularly since Alexander von Humboldt visited the island and carried out a variety of scientific experiments in June 1799. The singular geographical location and high mountains of the island make it an ideal place for meteorological and astronomic observations, as shown by the universal history of both scientific disciplines.

In the early years of the 20th century, the European scientific community showed a keen interest in setting up a permanent observatory on the mountains of the island. But the origins and creation of the Izaña observatory was steeped in arduous and, on occasions tense, negotiations in a convulse period of history, as were the times before the First World War, and laid a series of milestones in a variety of ways.

An observatory of this nature in the mountains of Tenerife, halfway between Germany and its colonies in Africa, turned out to be strategically placed to develop and support the German aeronautical and naval industry, as well as an unbeatable location in which to establish radiotelegraphic telecommunications, in their early years at that time.


The first meteorological observations

There is an actual, very interesting description of the understanding of the general circulation of the atmosphere by Leonardo Torriani. In the year 1592, the engineer from Cremona working at the service of Felipe II described the inversion of temperature at the summit of the island: “the air is so dry that I consider, according to my own experience, that a man could not be there over 24 hours. The winds there blow strong…and so I expect that it must be the highest part of the first region of air”.

The oldest scientific reference we have knowledge of dates back to 1645. At the time the Royal Society of London required a permit from the Spanish Ambassador in Great Britain for two members of the society to travel to the island’s peaks to “measure the weight of the air and the elevation of the atmosphere”. It should be remembered that just two years before, Evangelista Torricelli had taken the first measurements using a barometer of his own invention.

The regime of northeasterly trade winds, well known to Spanish and Portuguese sailors in the 14th century, was described in detail in 1686 by British astronomer Edmond Halley, who published the “First Wind Chart”. On his chart, Halley developed the first model of atmospheric circulation between the Equator and the Tropics, for which southwesterly wind observations were determining factors during summer at the peaks of Tenerife. This drastic change in direction from the Tenerife coast to the peaks was of great interest to scientists at the time.

In 1735 George Hadley, a curious British lawyer keen on meteorology, taking into account the subtropical latitude of the island of Tenerife, explained the dynamics of the atmosphere in the vertical component, also taking into consideration the rotation of the earth, to conclude that what is known as the “Hadley cell” is a determining factor in the general circulation of the atmosphere.

On 21st June 1799, Alexander von Humboldt ascended Teide taking measurements of air temperature and atmospheric pressure, as well as other observations of the island’s flora and vegetation. He was the first to determine the altitude of the sea of clouds – in summer above 1,150 m – and the principle causes of this: the humidity of the northeasterly trade winds and the effect of the island’s rugged terrain. However, given that no intermediate measurements were taken, he could not confirm the inversion of the trade winds.

Charles Darwin arrived in Tenerife with the ‘Beagle’ expedition on 6th January 1832. But he was unable to disembark due to a declaration of quarantine stating that the ship was carrying cholera from England. Nevertheless, Darwin took advantage of the occasion and documented the collection and measurement of the diameter of particles of dust in suspension, thus highlighting the importance of winds from the Sahara in the climatology of the islands.

The first work on the climate of the Canary Islands was written in 1823 by German geologist Leopold von Buch. In his book he systematised observations of the trade winds in the Canaries and at the peak of Teide carried out since Halley’s visit. He voiced the idea that counter trade winds descended to ground level near the tropics to then move towards the Poles, although he failed to explain the mechanisms of atmospheric circulation and the origin of the air feeding the trade winds.

In 1847 French scientists Arago and Desperray worked on a project to establish an observatory on Tenerife with the support of naturalist Sabin Berthelot, then French consul on the island. Interest in the project, in the words of Berthelot, lay “in the location of the island close to the tropics, in the altitude of its mountains and in the purity of its air for the realisation of excellent observations”.

During two months of the summer of 1850 Scottish astronomer Charles Piazzi Smith stayed at a mountain shelter, Altavista (3,252 m), close to the crater of Teide. He was the first researcher to set up permanently on the mountain, making the first systematic meteorological and atmospheric observations. Thanks to measurements made during two days of rapid ascent and descent, he discovered temperature inversion in the atmosphere above the humid layer of the trade winds. He also provided vital data on wind and climate at the peak.

When North American William Ferrel published his model of general atmospheric circulation in 1856, almost paraphrasing other, earlier scientists, he explicitly mentioned the importance of winds observed on the island of Tenerife. In his first theory of 1856, Ferrel presented an explanation for the southwesterly and northeasterly winds on Teide, to endorse his theory on the general circulation of the atmosphere, depending on the latitude, maximum values of pressure and the direction of the trade winds depending on the seasons. Ferrel’s interest in the higher winds at the peak of Teide lay in the fact that the mountain lies on the outer limits of the trade winds, and as that limit moves to the north or south, depending on the season, the northeasterly and southwesterly winds are alternatively predominant at the base of the mountain. Years later, in 1889, Ferrel, who like Hadley lent his name to a ‘cell’, simplified his theory on atmospheric circulation in the light of Thomson’s earlier study on the same subject.

Carl von Fristch, deputy director of the Central Institute for Meteorological and Geodynamics of Vienna (ZAMG), spent some time in 1864 studying and taking notes on the regime of trade winds and counter trade winds on the island. A number of years later, Julius von Hann, director of the ZAMG also published several studies based on observations of Tenerife.

A new and important series of tropospheric ozone measurements was carried out in the city of Santa Cruz de Tenerife in the winter 1862-1863 – certainly the first known study of its kind in Spain – with the aim of investigating and minimising the effects of an outbreak of yellow fever.

Years afterwards, in 1884, seventy-five observations of clouds carried out by Swedish Professor H. Öhrwall and Lieutenant Gustav Hultcrantz were picked up by Austrian meteorologist Julius von Hann. Through those observations the regime and direction of winds in the upper layer of the troposphere of the Canary Islands could be interpreted.

In 1888 Ralph Abercromby published an interesting article titled “Electric and Meteorological Observations at the peak of Teide”. He had been on the island in 1887 and also ascended Teide. Some years later, meteorologists Teisserenc de Bort and Hildebrandson published the International Atlas of Clouds, in which they used some photographs taken in Tenerife.

Based on the study “On the ultraviolet boundary of the solar spectrum, based on the plate negatives obtained by Dr Simony at the peak of Teide”, Frenchman A. Cornu published, in the year 1890, the first results on ultraviolet radiation measured until then.

Other studies and articles were published by European astronomers and meteorologists in the latter years of the 19th century - some of which were as renowned as that of Swede K. Angstrom, who published, in Upsala in 1895, the results of two summers’ work on Teide. Angstrom published his works under the title “The intensity of the solar radiation at different altitudes taken in Tenerife in the years 1895 and 1896”. K. Angstrom and his collaborator O. Edelstamm made a series of comparative measurements in proximity to the peak (3,692 m), at the observation site known as Altavista (3,252 m), on a site in Las Cañadas del Teide (2,125 m) and on a site on the coast south of Güimar (360 m). In addition to these results, in the annual report of the Swiss observatory Sonnblick of 1903, there is a comparison of the intensities of radiation observed at the peak of Teide and the values from the Swiss observatory measured by F.M. Exner.


The First Aerologic Observations in Tenerife.

The new methods of observation of the high troposphere using captive balloons and kites were developed towards to end of the 19th century and very soon a number of scientific campaigns arrived on the island of Tenerife and its waters, attracted by the location and terrain. The first and most notable of those scientists was Professor Hugo Hergesell, director of Strasbourg and Lindenberg Observatories from 1914, professor at the Universities of Strasbourg and Berlin, chairman of the International Commission for Scientific Aerostation (ICSA), in addition to being scientific advisor to Count Ferdinand von Zeppelin.

In August 1904 and April and September of 1905, Hergesell carried out his first sampling campaigns in Canary waters from on board the yacht “Princess Alice”, owned by his friend and colleague on scientific expeditions, the oceanographer Prince Albert of Monaco, the celebrated researcher who studied the currents of the Gulf Stream.

Another two pioneers of observations of the high troposphere, Frenchman Teisserenc de Bort – better known for naming the “Anticyclone of the Azores” – and North American Lawrence Rotch, visited Tenerife in 1905 and launched 40 captive balloons from Teide on the 8th, 9th and 10th of August. They also made a number of observations and atmospheric soundings over the sea from the vessel “Otaria” in February 1906. The main aim was to determine the influence of the terrain on Teide on the atmospheric circulation regime.

The first simultaneous surveys in Tenerife took place on 28th July 1908 and were carried out by Robert Wenger in the Orotava Valley and Hugo Hergesell, who worked at sea from the German vessel “Victoria Luisa”.

International interest in establishing a permanent observatory at the summit of Teide grew enormously during those years. And so Teisserenc de Bort proposed such an observatory to the International Commission for Scientific Aerostation (ICSA) when the commission met in Milan in 1906. The observatory would be part of an ambitious project to build a network of stations in the northern hemisphere. The Spanish delegation, represented by the colonel of engineers Pedro Vives y Vich, received the proposal from the ICSA and passed it on to his authorities, although it was received with little interest. Nevertheless, in the meantime, the interest and determination of the German government and imperial house grew substantially and, apart from their scientific interest, other, very different intentions soon became apparent.


The Spanish-German diplomatic conflict at the Monaco Conference.

Events occurred rapidly in the first months of 1909. In March of that year, two portable structures were to be transported to Las Cañadas del Teide, to a flat area located at 2,200 m above sea level, with the help of well-known local figures. These people intervened and, on behalf of Hergesell, and of another German scientist, Gothald Pannwitz, leased from the Orotava Town Council 25 hectares of land on a plateau at Las Cañadas del Teide. Meanwhile, Colonel Vives y Vich was on an official visit to Germany charged with learning of the latest progresses made in Europe in the field of aeronautics.

Once in Germany, Vives was informed by Hergesell of the immediate establishment of an observatory with “means provided by the ICSA”, and the support of the Spanish authorities was requested. But the truth was that no permit, not prior news about all those initiatives had been sent to the Spanish government, whilst the German had already started moving huge amounts of very expensive material and human resources for the observatory at Teide. Just a few days later, all the material was loaded at the port of Hamburg bound for Tenerife, including a wooden chalet donated by Kaiser Willem II, one of two residences used by the Kaiser himself on state visits made by train around Germany.

Chalet of Kaiser Wilhelm II of Germany. Circa 1910.


These events were rapidly transmitted to the Spanish government through diplomatic channels, and negotiations with the German government took place over the weeks that followed. At the beginning of March 1909, Hergesell travelled to Tenerife with all the material he deemed necessary and personally took charge of obtaining the pertinent permits from the local authorities for the establishment of the observatory at Las Cañadas del Teide.

Vives telegraphed Hergesell on 20th March to inform him that the Spanish government had itself taken the decision to construct an observatory on Tenerife, and wished to cooperate with the ICSA on the preliminary works. Hergesell, at that moment in Tenerife, prepared to return as he would chair the next ICSA meeting, to be held in Monaco on 31st March. However, instead of travelling to Monaco directly, Hergesell held a private meeting in Madrid with Colonel Vives and the Spanish Minister of State on 28th March.

The result of the negotiations would finally be announced at the VI Conference in Monaco. Hergesell would there announce that the use of one of the two buildings “donated by the Emperor of Germany” would be provisionally ceded to the Spanish government. Colonel Vives, as the official Spanish delegate, would announce that the Spanish government had taken the decision to construct a permanent Spanish observatory on the peaks of Tenerife, to be complemented by another at sea level.

But the date for the session arrived, on 6th April, when, according to a private letter from the Minister of State, Manuel Allende Salazar to the Spanish ambassador in Germany, dated 10th April 1909, “the establishment of the Tenerife Observatory was discussed, which led to some incidents of note. The Chairman of the Congress, Dr Hergesell had reached an agreement with Colonel Vives regarding the provisional ceding of the barracks, the exclusively Spanish creation and operation of the observatory, all in compliance with the officer’s orders. However, at the last moment Hergesell requested Colonel Vives meet with a high ranking member of staff of the Prussian Interior Ministry, who had arrived in Monaco exclusively to deal with the matter [underlined in the original]. Colonel Vives hesitated a moment, but finally accepted the proposition in the belief it was a means by which to learn of Germany’s intentions; and, effectively, on reading the pages on which Spain’s decisions were detailed, which Hergesell had previously found acceptable, the Prussian functionary objected claiming that, in exchange for the use of the barracks, Spain should commit to leaving two places at the observatory available for use by two male scientists. Colonel Vives vigorously opposed the suggestion informing the representative of the German Ministry of the Interior, that Germany could keep the barracks Spain had not asked for in the first place. The gentleman then attempted another approach to the matter and proposed the issue not be brought before the congress, but that Germany would arrange to seek a solution to the matter with Spain through their ambassador in Madrid. Aware of the advantage to be gained from having the Spanish proposal approved by the International Congress, with the acquiescence of the delegates from the different nations, Colonel Vives protested strongly against the Prussian functionary’s proposition, arguing that as the matter was on the agenda and a Spanish representative having travelled to attend the congress with the sole purpose of dealing with an issue of such interest to our country, it would be an informality – no, a snub to abandon the matter; and he insisted it be dealt with in the session, otherwise he himself would bring the matter up (…). On hearing of these extremes in the congress, the delegates present awarded Colonel Vives a standing ovation – even some of the Germans with a vested interest in science, such as Dr Assmann; the Italians, French and North Americans stood out for their expressiveness (…). If the tale above related is anything to go by, Spain is, now more than ever, obliged by national propriety to carry out, in the short term, the observatory projected, whose installation and services must not require from third parties major expenditure”.

The course of diplomatic negotiations started by the Spanish government was the only course possible, once Hergesell had leased the land in Las Cañadas under local municipal laws of the time, albeit in his own name and not as chairman of the ICSC. Although the matter was discussed at the highest levels politically of both governments, twice at cabinet meetings, once in parliament and another in the council of state, the result reached by the governments would be published as the result of exclusive international scientific cooperation.

Even more important, to construct Izaña observatory and to staff it with duly qualified personnel, royal decrees to the effect were dictated in 1912 and 1913, the second of which was to create the, as yet inexistent, staff of meteorologists and meteorological assistants.

Previously, in October 1911, a scientific committee from the National Geographic Institute had travelled to the island of Tenerife with the aim of finding the most appropriate location for the future observatory. The mountain of Izaña was chosen for the purpose, on the summit of a ridge dividing the island into two parts marked by the presence of wide valleys, 2,367 m above sea level. The previous German observatory at Las Cañadas del Teide had surprisingly been placed on a plateau sheltered from the wind. As became evident years later, when in the year 1920 Transmediterranea Airline Company took over the Seville-Buenos Aires air route, the primary interest of the Germans was, amongst others, to study the meteorological characteristics and the suitability of Las Cañadas del Teide for use and exploitation as a Zeppelin aerodrome.

The project for Izaña observatory was presented to the ICSC at the conference in Vienna in 1912 by the new director of Meteorological Services, Jose Galbis, who took an active part in the project.

During those years Garcia-Lomas and two assistants posted to the now Spanish observatory, collaborated with the members of the German expedition and a considerable number of foreign scientists. Professor Lüdeling and Dr Luyken of the Köeniglich Meteorological Institute, Dr Dember, professor at Dresden’s Physics Institute, Martin Uibe and W. Buchheim of the University of Leonardville made observations of atmospheric electricity, magnetic declination, ultraviolet solar radiation, polarization of sunlight, atmospheric ionization, optics, etc. in accordance with the quality of their results, they pointed out that, due to the absence of dust and mist, “Teide was preferable for physics and astrophysics investigations over the mountains of Switzerland and Italy.”

In 1913 the permanent German scientists in Tenerife moved out of the provisional observatory at Las Cañadas del Teide, and Garcia-Lomas took charge, although other new investigators continued to visit. However, activity at the observatory stopped completely at the onset of the First World War and when the observatory at Izaña was inaugurated in 1916, the facilities at Las Cañadas del Teide were definitively abandoned.

Building an observatory on the peaks of Teide turned out to be a complex, expensive task for the Spanish government. Construction work suffered delays and was further complicated by other, endless delays of the administrative, political and economic kind. The work lasted four years and cost some 150,000 pesetas of the time. Finally, the observatory at Izaña was inaugurated on 1st January 1916, and has gone on operating since then without further interruption.


The Izaña Observatory. Circa 1930.



Izaña Observatory after construction

The moment in history when the observatory was inaugurated was not exactly the best in terms of international cooperation. The war in Europe put a stop to campaigns and European scientific visits, particularly those of the Germans, who were impeded from carrying out any activity outside of German territory by the Versailles Treaty in 1919.

The war in Europe completely halted visits from foreign scientists. In the years after 1914, activity at the observatory was reduced to little more than conventional aerologic observations and measuring radiation levels. In the decade between the 40s and 50s, Canary meteorologist, Inocencio Font published the best and most varied works and articles on the climatology and meteorology at Izaña, as well as rather interesting studies on winds at altitude based on soundings carried out between 1916 and 1935. Some German scientists, von Ficker, Roschkott and Müller amongst others, published similar works.

Scientific activity practically came to a standstill during the period 1930-1960. The consequences of the Spanish Civil War and the Second World War were hard-felt in terms of material and human resources, causing the almost complete absence of special investigations.

Meteorological sounding with kite at Izaña. Circa 1950



Aerologic soundings, using kites and pilot balloons were suspended in 1960. The advantages of launching them from mountain observatories were no longer there and radiosondes came into use from the city of Santa Cruz de Tenerife.

In 1958, coinciding with the political opening of the Franco regime and the celebration of the International Geophysical Year (IGY), foreign scientists once again began to arrive at Izaña on the occasion of a solar eclipse. Astronomers and astrophysicists used the observatory to carry out studies on the transparency of the atmosphere and to examine the degree of suitability of the place for astronomic observations.

In October 1968, a team of meteorologists from the University of Mainz, led by Prof. Christian Junge, stayed at the observatory to test and validate new instruments with which to measure and analyse atmospheric background contamination in the troposphere from on board the vessel “Meteor”, an oceanographic and meteorology research vessel that would be carrying out a campaign in North Atlantic waters.

In the summers of 1973 and 1974, a series of soundings was carried out at Izaña to study atmospheric micro-turbulences, given their huge importance to astrophysical observations. Other studies on the transport of aerosols and other chemical components in the atmosphere took place at the observatory. Based on results obtained from a campaign to measure halocarbons carried out in 1979 by Dr R.A. Rasmussen of the Oregon Graduate Center for Study and Research (USA), Dr Rasmussen wrote a letter to Dr Miguel Zalote, at the time director of the observatory at Izaña, in which he said “data we have obtained at Izaña is the best in the world”.

Other new studies on the transportation of aerosols and chemical components in the subtropical troposphere were carried out at the observatory by Professor Joseph Prospero, of the University of Miami, at the end of the 70’s. These surveys would eventually, in 1987, become part of the AEROCE (Atmosphere/Ocean Chemistry Experiment) for atmospheric research in the North Atlantic region.

Once again the interest of the Germans in the natural conditions at the observatory at Izaña was renewed. In 1981, Drs R. Schmitt and Balchtrusch, commissioned by the German meteorology service, carried out a variety of tests to evaluate the suitability of the observatory as a BAPMoN (Background Atmospheric Pollution Monitoring Network) station, representative of the free atmosphere in the subtropical region of the northern hemisphere. In 1984, some 75 years later, the Spanish and German governments signed an agreement of cooperation under which the observatory would join the World Meteorology Organisation’s BAPMoN programme.

In 1989 the BAPMoN network was merged with the GO3OS (Global Ozone Watch System) network to constitute the GAW (Global Atmosphere Watch) network, of which Izaña is one of the principal stations.