Ship's logbooks historical wind observations for the open oceans

Abstract

Along the fifteenth century, Europeans started the open ocean navigation towards their colonies. This required the daily determination of longitude and latitude, which were recorded jointly with meteorological observations in the ships logbooks. Historical wind force observations were not instrumental but estimated and codified as “wind descriptors” in the logbooks. On the other hand, wind direction observations do not suffer from such limitation as they were measured with a compass and hence can be considered a truly instrumental observation, even for the oldest records. Millions of pages of such records have been preserved in different archives. They represent a valuable resource and provide unique information for an area of the globe poorly covered (the oceans) and for a period (c.1680- 1900) when weather observations are sparse. We will show that logbooks extend back the instrumental record with observations of comparable quality to the modern ones, thus reducing the limitations derived from the shortness of current records. This has allowed building centennial series which allow a better characterization of weather extremes and unveiled multi-decadal variability previously unsuspected. We will provide examples as the steady enhancement of the Australian monsoon since the early 19th century, the non-stationary behavior of the Euro-Atlantic atmospheric circulation during the Late Maunder Minimum, the alternation of wet and dry multidecadal periods in the Sahel or the complex relationship between the Western North Pacific Summer Monsoon and the different ENSO modes. Finally, we will describe the status of the UPNAO project, which is currently recovering data from the Eastern Tropical North Atlantic.