New Meteorological Observations Recovered from the Lighthouses on the Northern Coast of Catalonia (1853–1956)

The recovery of past meteorological data is essential for understanding the evolution of climate over time and detecting patterns of climate change. These historical records, often stored in physical or handwritten formats, provide valuable information for analyzing long-term trends, comparing extreme events, and validating current climate models.

The Meteorological Service of Catalonia, in collaboration with the Historical Archive of Girona, has catalogued and digitized a previously unpublished documentary collection that includes weather observations from a group of nine lighthouses located along the northern coast of Catalonia (in the province of Girona). The archive spans the period from 1853 to 1956, and a total of 44,168 images have been taken. This study provides a description of the archive and its potential uses.

The documentary collection is quite diverse, as it covers nearly a century. Generally, however, it consistently includes daily or sub-daily (three times a day) information on non-instrumental variables: sky conditions, wind direction and force, sea conditions, and visibility. For visibility, the observation of neighboring lighthouse lights was recorded, which makes it relatively easy to determine horizontal visibility in kilometers. In the case of sea conditions and wind force, the terminology used during the nineteenth and part of the twentieth century does not follow the international scales that later became widespread, but rather uses local terms, which will need to be standardized and harmonized. From the late 1890s onward, the lighthouses began incorporating instrumental observations, especially of extreme temperatures and daily precipitation. In some cases, such as the Sant Sebastià lighthouse (located in Palafrugell), the records include additional variables: atmospheric pressure, average wind speed (measured with a totalizing anemometer), and meteorological phenomena. From this period on, a series of daily report sheets also appear, detailing storms (start and end times, presence of lightning, hail, etc.). The collection also includes extensive correspondence between the lighthouses and the ministry responsible for public works.

The recovery of this archive will make it possible to extend already identified instrumental series and to analyze in greater detail and with greater accuracy the characteristics of maritime storm events in this part of the western Mediterranean. It will also help to contextualize these events in terms of their intensity, frequency, and duration, both in relation to current observations and to future projections from climate models.