Met. logs in the National Met. Archive

The NMLA holds an extensive collection of meteorological logs from the UK VOS fleet. These logs vary enormously in content and format, but typically contain records of pressure, air temperature, wind speed and direction, sea temperature, and often other variables, every few hours.

Sample page from a ship’s Met. log

It is difficult to tell how much of this archive has been digitised, because although the observations (sea-temperature etc.) taken from these logs have made it into ICOADS, those observations have very little attached metadata indicating where they came from. Comparing samples of the NMLA met. logs with ICOADS suggests that almost all of the meteorological logs in the NMLA have had some data digitised from them, but that this digitisation was very incomplete - not all variables, not all observing times, only a subset of dates or locations - and the data is often imprecise, with positions rounded to 1 degree, for example. In addition to these limitations with the digitised data, the absence of good metadata also limits the value of this earlier digitisation - if we can’t link an observation to a log or even a ship, it is very difficult to assess the necesary bias adjustments.

We should aim to re-digitise all this material - this would propably at least double the number of observations available, and those observations would be more precise and more useful.

Some work has been done on this source. Clive Wilkinson has produced catalogues of Antarctic and China Seas logs in particular, and thousands of pages of those logs have been photographed. Some of those Antarctic logs are currently being digitised through the citizen science project Southern Weather Discovery. But it’s unlikely that this approach will be fast enough to digitise the whole archive, we will need to come up with something better.