You’ve probably noticed that we’ve published another instalment in the ongoing series of Royal Navy logbooks on oldWeather. For those keeping count, this is batch four of oldWeather phase two, and the unifying theme of this group of books is that the ships travel far from home indeed – these are voyages that include operations in the Pacific.
There’s the usual range of ships to choose from, from the Battlecruisers Renown and Repulse, to the Torpedo Boats and Gunboats doing inshore work in China; all of them helping to map the climate of an ocean that was named for its good weather, but does not always live up to its name.
We expect these logbooks to describe operations in the Pacific, but of course we won’t really know what they are up to (and where) until we’ve read them. So expect a Surprise – even if you don’t earn a Post as Captain, maybe you’ll read of a voyage past Mauritius, or Desolation Island, or encounter some strange Fortune of War on the way to the Far Side of the World.
Now that we’ve completed the original batch of logs we were working on in oldWeather, we’ve started to release the new weather observations recovered for use in scientific investigations. Leading the way in such investigations is Ed Hawkins of the University of Reading, who’s started a series of posts on his blog describing the value of oldWeather for the study of Arctic climate and sea-ice, the North Atlantic Oscillation, and reducing uncertainties in Atlantic pressure fields.
For the last few weeks we’ve been watching the ‘% completed’ figure on the Old Weather front page creep ever closer to 100. We’re very close to completing the task we took on on October 12th, 2010, by transcribing every single log page (750,000 transcriptions). That’s an awesome achievement – take a moment to feel the victory.
But we’re not ready to decommission the project – there’s more yet to learn about the climate and the history of the early twentieth century. There are many logs in the National Archives that we’ve never looked at: some from our old friends, and some from new ships we’ve never before followed. So with support from JISC, we returned to the National Archives, camera in hand, to collect a new set of logbook images – and we’re launching the first batch of them today as the start of oldWeather phase II. (There will be more to come).
This first batch of new logs is timely for those of us in the North, feeling the cold of winter set in, because these are voyages in the Mediterranean. Forget the chill and the dark, and travel vicariously through warm and history-filled seas. If you have fond memories of a previous voyage on HMS Africa, Britannia, Caesar, Liverpool, or Theseus; furlough is over, your ship needs you – please report to your former station at your earliest convenience. If you are looking for new company and new adventures, HMS Aphis, Ark Royal, Barham, Ben-my-Chree, Blenheim, Canterbury, Castor, Galatea, Grafton, Minto, St George, and Warspite launch today for the first time with us. The point of departure, in all cases, is http://oldweather.org.
We started our voyage one year ago (12th October 2010), and we’ve come a long way since then. According to the standard baby development milestones, we should now be able to explore new objects by poking with one finger, crawl up and down stairs, and reach out and grab things we want.
That article seems to have left out the standard ages for ‘transcribed 685,000 log pages’, ‘generated one million new historical weather observations’, and ‘built a thriving community of 10,000 historical climatologists’. But I think it’s safe to say that not many one-year-olds have achieved as much – we are remarkable indeed.
Happy birthday oldWeather, it’s been a treat to grow up with you. And in common with most people of our age, I look forward to exciting new development in the near future.
Oldweather is steaming past milestone after milestone, and a few days ago we passed a big one : 150 ships complete. That is; 150 ships, from Acacia to Wonganella, have had all of their log pages for the period transcribed by at least three people. That’s 89,000 pages of new information for climate and historical research.
To mark the completion of 100 logs, we made a movie showing the ships bustling about across the world’s oceans. Rather than updating this with the new information, I thought I’d be a little more ambitious and show the transcribed data in a more comprehensive and interactive format.
I’ve long been an admirer of Google Earth – a geospatial data viewer that’s powerful, easy to use, and, most important, free to download and use. If you haven’t played with it I urge you to give it a try – download a copy and have a look at the satellite’s-eye view of your favourite places. But the real charm of Google Earth is that we can add our own data as overlays. It works very well for following ships; and I’ve made an overlay from the 150 completed oldWeather ships.
So once you’ve got Google Earth, download the overlay and have a look at what you’ve created: select a ship from the list on the left, pick a time using the slider at the top, and click on the markers to see the day’s records for that ship. The user interface takes a bit of getting used to, but with practice you can make your own animations.
I included as many of the transcriptions as I could, but there are some that I haven’t yet managed to convert into this format. So if you can’t find something you know you entered, don’t worry: we haven’t lost it. It will take a little longer, but we will make it all available.
Edmond Halley is best known for his comet, but he was one of the great polymaths – as well as making astronomical discoveries he was also a notable meteorologist: he did important early work understanding the trade winds and monsoons. It’s less well known that that he was also a Naval Officer: in 1699 he was granted a commission as captain in the Royal Navy, and he commanded HMS Paramour (a pink) on an expedition into the South Atlantic to investigate the variation of the compass.
His main concern was with magnetism, but as a man of wide interests, Halley took with him examples of those two exciting modern scientific instruments: the thermometer and the barometer. I can’t find the logbook of the voyage, but Halley’s notes have survived: they were published by Alexander Dalyrmple, in 1775, as part of “A collection of voyages chiefly in the Southern Atlantick Ocean“. They date from 220 years before the logbooks we’re used to in OldWeather, but to anyone who’s looked at our logbooks they are oddly familiar: records of latitude, longitude, wind force and direction and, in the left-hand margin, thermometer and barometer readings.
In 1699 the barometer had been around for more than 50 years, and the barometer records in Halley’s account are clearly in the familiar inches of mercury. But the thermometer did not become a reliable, precision instrument until about 1725, when Fahrenheit invented the mercury thermometer with a standardized, calibrated scale. So when Halley says the temperature is ’33’ it’s not immediately obvious how this should be interpreted. Careful scholarship has established, however, that Halley was using a thermometer designed by Robert Hooke, and lavishly described in his book Micrographia:
The Stems I use for them are very thick, straight, and even Pipes of Glass [...] above four feet long [...] [filled] with the best rectified Spirit of Wine highly tinged with the lovely colour of Cocheneel, which I deepen the more by pouring some drops of common Spirit of Urine, which must not be too well rectified, [...]
From Hooke’s description we can convert Halley’s reported units into modern equivalents at least approximately – Halley’s ’33’ was about 8°C.
The diary entries are mostly routine accounts of the movements of the ship, but occasionally he puts in longer and more interesting reports: here’s an example from Thursday 1st February 1700, when they were close to South Georgia, in the cold waters of the Southern Ocean:
[...] between 4 and 5 we were fair by three Islands as they then appeared; being all flat on the top, and covered with Snow milk white, with perpendicular Cliffs all round them [...] The great height of them made us conclude them land, but there was no-appearance of any tree or green thing on them, but the Cliffs as well as the tops were very white, our people called A by the name of Beachy-Head, which it resembled in form and colour. And the Island B in all respects was very like the land of the North-foreland in Kent, and was at least as high and not less than 5 miles in front, [...]
The following day they were disconcerted to discover that these ‘islands’ had moved, and fled north to warmer waters. This is the first recorded sighting of a tabular iceberg.
Halley’s observations are probably not of great value to climate scientists: his instruments were state-of-the-art for 1699, but it took decades longer for such observations to became accurate and plentiful enough for climate reconstructions. He did set a precedent though – possibly as the first person to go to sea with a barometer and a thermometer – and we’re still following his example more than 300 years later.
When scientists talk about pressure, they measure it in Pascals (Pa: the SI unit for pressure). For atmospheric pressure, 1Pa is an inconveniently small number, so we lump them together in groups of 100 and talk about hectopascals (hPa: 1hPa=100Pa). The atmospheric pressure at sea level is usually given as 101325 Pa, which is approximately 1000 hPa; so 1 hectopascal is also referred to as 1 millibar – when you hear your weather forecaster talking about millibars, hectopascals are what he’s really using. The ships, however, don’t measure pressure in hectopascals or even millibars; they measure it in inches. This is an artefact of the way they measure the pressure – with a mercury barometer.
Back in the early 17th century there was much discussion among the scientists of the day about why it was impossible to pump water more than about 10m upwards. It was Evangelista Torricelli, in 1643, who realised not only that the height to which the water rose was determined by the weight of the surrounding air, but also that you could use this effect to measure changes in the air pressure. A 10m column of water is a nuisance to work with, so he switched to the much heavier mercury as his working medium, and made the first ever barometer measurement.
We’ve been measuring air pressure in the same way ever since – balance the weight of a column of mercury against the weight of the surrounding atmosphere, and the taller the column the higher the atmospheric pressure. At sea-level, the column will be about 76cm (29 inches) high, and the changes in atmospheric pressure as the weather changes cause fluctuations of up to a few inches. The pressure is proportional to the height, so we can get the pressure in hPa by multiplying the height in inches by 33.86389.
Of course, making precise measurements requires great care (very pure mercury, no air in the tube, careful calibration, …) but by our period (1914) barometer manufacturers were making very good instruments. There are, unfortunately, still a few complicating factors which we need to be aware of:
- The weight of a column of mercury changes with temperature – the weight of 760mm of mercury is less when it’s hot than when it’s cold, so we need to adjust for this when calculating pressure from height. A further complication is that the column height is usually measured using brass measuring rods, and the length of brass rods also changes with temperature. So we apply a correction from a table or an empirical formula – these tables vary slightly depending on the barometer design, but in OldWeather we don’t usually know the make of barometer in use so we use a generic table. To make this temperature correction we need, of course, to know the temperature of the barometer: Almost all mercury barometers have a thermometer attached and it is usual to record the barometer height and attached thermometer temperature together – as is done in many of our logs. Moving from 0C to 35C (Arctic to the tropics or February to July in the UK) would introduce a change of about 0.5% (2 tenths of an inch).
- The weight of a column of mercury changes with latitude. We launch satellites from French Guiana, rather than Europe, because satellites weigh less in French Guiana than they do in Europe. Moving from Plymouth to Singapore would reduce your weight by about 0.2% (about 8 hundredths of an inch)
- We generally want the pressure at sea-level. We usually keep the barometer above sea-level, so we need to add a little to the pressure to adjust for this. Every 80 or 90 feet above sea-level reduces the pressure by 1 tenth of an inch.
- It’s usual to measure the position of the top of the mercury column. As the mercury rises in the tube, the level of the mercury in the cistern at the bottom of the tube will fall. Because the mercury column balancing the atmosphere runs from the top of the level in the tube to the level in the cistern, we need to add a little to measured height changes to allow for this.
- If the glass tube containing the mercury column is narrow (to reduce weight and to damp oscillations) the height of the mercury will be reduced by capillary action. We need to add a little to the measured height to allow for this.
We call these, respectively, the temperature correction, the gravity correction, the height correction, the capacity correction and the capillary correction. By 1914, with a good barometer, the last two should have been allowed for in the instrument’s calibration and operation, and the third is small for ships, but we still need to make the first two corrections. The changes involved are small compared with the changes associated with short term weather, but they are important for correctly representing the more subtle, longer-term changes.
Mercury barometers are great for fixed, stable, weather stations. They are however expensive, difficult to read accurately in a ship in motion, a terrible nuisance to carry around, and really too fragile for service in a warship. So much ingenuity has been spent on devising cheap, portable, alternatives. The aneroid barometer is essentially a sealed metal bellows that grows and shrinks as the air pressure rises and falls, coupled to machinery to amplify its movements and display them on a scale. These first appeared in 1843, but it took a long time to make them accurate and reliable enough for serious use. By 1914, however, they were coming into use, and it’s clear from the logs that our ships used both mercury and aneroid barometers. Aneroids don’t require gravity, capacity, or capillary correction – and are mostly deliberately designed to be insensitive to temperature changes, so they don’t need an attached thermometer measurement. Nowadays aneroid barometers report pressure in hPa, but back in 1914 most gave readings in inches of mercury. So far I’ve only seen one ship reporting pressures in hPa – HMS Glowworm.
Were the aneroids on our ships less accurate than mercury barometers? more accurate? different in some subtle way? I don’t know – but I look forward to finding out. So if you see any reference in the log to the type or make of barometer in use, please transcribe it. We don’t need to know what they were using, as we can guess with good accuracy, but it does help. A few ships record both mercury and aneroid barometer readings – if you see this, please transcribe both of them; the comparison between them helps us estimate the accuracy of the measurements.
Remember the fog of ignorance – the uncertainties in global weather reconstructions that our new observations will help to clear away? Here’s another view of the problem (click on the image to see the movie version).
The skill with which we can reconstruct past weather depends critically on how many observations of it we have, and for the period we’re investigating in Oldweather, it varies a lot from place to place: in the UK and US we can do reconstructions precisely, but for much of the rest of the world – the southern hemisphere in particular – we’re still very uncertain.
So how much improvement do we expect when we add our new observations to these reconstructions? Obviously this depends on where the new observations were made, and on how good they were, so it’s interesting to compare a few, from a range of times and places. I chose to follow the battlecruiser HMS New Zealand on her circumnavigation in 1919: comparing, at every point in the voyage, her observations of the weather (air pressure) with the existing reconstruction – our best estimate of the weather before Oldweather.
The New Zealand started her trip in Plymouth in February, where we already knew that the weather was miserable – the thinness of the blue line means that we already had enough nearby observations to be sure of the weather, and the spikes in the pressure series are depressions blowing through. The good news is that the ship’s observations agree almost exactly with the reconstructions using other records, which means that the New Zealand was making good observations – they’d calibrated the barometer correctly and were careful in their measurements.
Almost as soon as the ship leaves the UK, the blue line widens – our reconstructions are less certain of the weather. it also gets less variable, as they are sailing in the more stable weather of the tropics. The best illustration of the value of the new data, however, comes in the southern hemisphere: for Australia we already have some observations, so our reconstruction was fairly well constrained already, but New Zealand (the country) was deep in the fog of ignorance, and the wide blue band at that point shows the huge uncertainty in the local weather – an uncertainty that we’re now able to remove using the new observations from New Zealand (the ship).
It will be a while before we can make another global weather reconstruction that includes our new Oldweather observations (that’s a major project taking lots of supercomputer time), but plans for doing it are well advanced. When we’ve done this, and I’m able to repeat this analysis using the resulting reconstruction, then the weather will be precisely known all along the route of the ship (the blue band will be thin at all points) and New Zealand (the country) will have emerged from the fog of ignorance – it’s weather conditions will be clearly known.
Which is only fair, as the New Zealanders paid for the construction of the eponymous battlecruiser in the first place.
Working with the logbooks has done wonders for my knowledge of global geography. If it’s at sea level, one of our ships has probably been there, or at least mentioned sighting it on the way past, and we can travel, vicariously, with them; from Abadan to Zanzibar by way of Cockatoo Island, Fernando Po, Nuku’alofa, Surabaya, and Wuhu (with assistance from lighthouses on Mwana Mwana, Muckle Roe, and Makatumbe).
We’d expect the Royal Navy to spend most of their time in British ports, but we deliberately chose the logs we’re looking at to include those going foreign, and omit the stay-at-homes, because this gives us better information on global weather. This choice means that foreign ports are the most frequently mentioned in our logs. In the 300,000 or so log-pages we’ve looked at so far, Hong Kong tops the ‘most visited’ table (with 23,000 mentions), followed by Bermuda and Shanghai. The first UK port comes in fourth: Devonport (6000 mentions) and though most of these are for the UK naval base near Plymouth, its statistics are boosted by the existence of another base of the same name in Auckland.
The existence of two Devonports highlights a difficulty we run into in using the port names. When the ship is in port, and sometimes when it is operating close to land, the port name or landmark is the only information we have on the ship’s location. So we have to convert the name into a latitude and longitude, and this can be challenging. For many ports a position is not hard to find: Gibraltar, Bombay, Glasgow and Aden are all well known. Many more are only a quick web search away: Esquimalt is on Vancouver Island, Thursday Island is in the Torres strait, and Walvis Bay is in Namibia.
After that it gets harder – East London is nowhere near East London, St Vincent usually means Cape Verde, rather than the identically named place in the West Indies or the Portuguese headland made famous by the battle of 1797. ‘No. 10 dock’, ‘No. 5 buoy’, and ‘No. 7 warf’ are all in Plymouth, but ‘on patrol’, ‘southern base’, and ‘on surveying ground’ could be anywhere.
The Navy are renowned for their courage and seamanship. Their orthography and penmanship are a little more variable, so we have Wei Hai Wei (2345 entries), Wei-hai-wei (1357), Wei hai Wei (633), Wei hai wei (314), Wei-Hai-Wei (231), wei hai wei (91), wei lai wei (69), Weihai wei (57), wei-hai-wei (53), Wei hei wei (33), Wei-hei-wei (32), WEI HAI WEI (30), and even W.H.W (26) – all of which are references to the same place.
With the technology of 1914-22, sorting all this out into a set of positions would have been a terrible job; but modern internet search engines, atlases, encyclopaedias and gazetteers are very powerful tools for tracking down obscure and badly spelt place-names. Today I’m particularly grateful that I live in the future.
I was really excited to see, a few days ago, that we’ve now completed the logs for 100 ships (100! and that only includes those where every page has been looked at by at least three people – there are many more making good progress). So we’ve now got enough information to look at the results from the fleet as a whole, as well as individual ships.
As one way of doing this I’ve made a video showing the ship movements from all the completed pages so far: Every point is one digitised weather observation, coloured by pressure (red=high, blue=low). At 10 days a second it takes 5 minutes to get through 1914-22, but there’s plenty to see – I like such visualisations because they always bring out new information:
Apart from the weather information (watch the sporadic outbursts of widespread low pressure – bad weather – in the North Atlantic), I like the way one ship settles in Bermuda – apparently determined to watch out the whole war from there; I bet that’s a very desirable posting. It’s also notable how big an effect the war apparently has on the patterns of movement – there is an explosion of activity in August 1914 and a clear reduction in late 1918. The war gets very little mention in the logbooks, but our results still indicate that it had a big impact on the activity of the ships.
We can also see a few cases that require more quality control: there are a few ships travelling through the Sahara, the Amazon and the Greenland Ice-cap – these are probably position errors in the logbooks. I think the ships in inland China, however, are the river gunboats about their proper business.