Recovering, correcting and reconstructing precipitation data affected by gaps and irregular readings: the Padua series from 1812 to 1864

The aim of this work is to reconstruct the 1812-1864 period of the Padua precipitation series, affect-ed by some biases, e.g. missing readings and cumulative values, as in this period the observers did not follow a precise protocol: the measurements were not taken at specific hours of the day, it may happen that the raingauge was read after some days, cumulating rain, or even the precipitation was not recorded at all. Therefore, the daily amount and the frequency reported in the Log are not ho-mogeneous with other periods, and need correction. The correction methodology has been based on the daily weather notes written in the Log in parallel to the readings. Taking advantage of the peri-ods in which both weather observations and instrumental readings were regularly taken, the terms used to describe the precipitation type and intensity have been classified, analyzed statistically, cali-brated, and transformed into numerical values. The weather notes allowed to distribute the cumula-tive amounts collected during some consecutive rainy days into the likely precipitation occurred in every single rainy day. In the case of missing readings, but in the presence of weather notes, the missing amounts have been estimated using the relationships found between precipitation types and amounts. Finally, the recovery of additional contemporary documents made it possible to fill some gaps of this period.