A new meteorological record for Cadiz (Spain) 1806-1852: Implications for climatic reconstructions

Abstract

A new documentary source of data for wind, atmospheric pressure and air temperature for the city of Cadiz (southern Spain) has been abstracted, analyzed and compared with present-day data. Wind records cover the period 1806-1852 with three observations per day. Instrumental pressure and temperature cover the period 1825-1852. While the historical pressure series shows average values very close to that found for the period 1971-2000, temperature shows a large asymmetric seasonal warming, with increments in the order of 2 degrees C for the winter months and almost no change for summer. Wind measurements have been transformed into their numerical equivalents and then compared with present-day values. The analysis shows that the numerical estimation of ancient wind forces observed at Cadiz, while providing a robust climatic signal, has a strong bias to larger values than their instrumental equivalents. Despite the uncertainties involved in the interpretation of early wind series, this effect could be related to the recording of "average wind gusts" rather than average winds as measured by today's anemometers. In consequence, wind climatologies based on historical data, which recently are becoming available to the scientific community, should be used carefully.