An examination of the accuracy and consistency of ships' logbook weather observations and records

Logbooks have survived in large numbers and contain notable quantities of climatological information. This paper examines the degree to which these data are reliable and consistently recorded. This is done by comparing the daily observations entered in the logbooks of vessels sailing in convoy, at which times the respective ships' officers would independently estimate and record the prevailing wind force and wind direction. The results are described using a variety of descriptive summary statistics. In general, wind force records are highly correlated and wind direction differences are relatively small compared with the natural variability of this phenomenon. Wind directions were studied and found to have a bias towards 4-, 8- and 16-point compass readings at the expense of 32-point readings. Corrections were needed to convert the recorded directions, which were made by reference to magnetic north, to their true north equivalents.