Early Meteorological Observations in Almada (Portugal) for the Period 1788-1813 by Medical Doctors

Early meteorological observations have been found for the period 1788-1813 in a collection of historical documents entitled "Medical and meteorological observation books" (Livros de observacoes medicas e meteorologicas) that is preserved nowadays in the Municipal Historical Archive of Almada. Almada is a Portuguese city located on the southern bank of the Tagus River, near the mouth of the river, in front of the capital city of Lisbon, which is located on the northern bank. In this work, more than 5000 meteorological readings for the period 1788-1813 have been recovered and analyzed. Daily values have been preserved for the period 1788-1789. However, only monthly values have stood the test of time for the period 1792-1813. The meteorological variables recovered are temperature, pressure, wind direction and the state of the sky. A quality control was carried out to find possible errors, either in the original data or in the digitization process. Unfortunately, there is no information in the metadata about the instruments or the observational methodology. Pressure and temperature data from modern and reanalysis datasets were used as references to study the agreement between these datasets and the Almada dataset. Daily pressure and temperature values from the Almada dataset were used to study, in particular, the meteorological conditions of the winter of 1788/1789 in Almada because this season was one of the coldest in the last 300 years in Central Europe. The complete dataset of early meteorological observations in Almada is freely available to the scientific community.