Author Topic: Stanley to Archangel, and all points in between.  (Read 3179 times)

philip.brohan

  • Old Weather Team
  • Full Member
  • *****
  • Posts: 164
    • View Profile
Stanley to Archangel, and all points in between.
« on: February 03, 2011, 02:21:20 pm »
It probably won't surprise many of you to hear that hear that the Earth is generally warmer at the equator, and colder towards the poles. I base my holiday plans heavily on latitude: going north (from England) for snow, and south for sunbathing. We all know this, but OldWeather has now completed enough log pages that we can prove it just from the logbook observations - the image below shows how air temperature changes with latitude, using the 120,000 temperature observations from pages that have already been examined by the three people we need to provide reliable results.


So it's warmer (on average) in Singapore, and colder in Scandinavia; we didn't need the logbook records to tell us that, but that doesn't mean that this way of looking at the data is not interesting - partly because comparing the temperature records with others made at the same latitude is a good way of finding outliers: values that are likely to be errors in either recording or transcription.

One thing we can immediately see from the figure is the spikes at locations associated with ports. The spikes go both up and down, meaning there more of both high and low temperatures at these locations. Partly this will be a a physical effect - temperatures over land do vary more than those over the ocean - but it's also partly an artefact of the way I've made the plot: The Navy ships spend a lot of time in port, so we have many more observations from those locations, and so more unusually high or low values. Even in the ports, however,  there are very few really way out values, but some are suspicious: are there really marine temperatures below 0F at about 45N? (Seawater freezes at 29F) Those values come from HMS Bayano, off  the Canadian coast in December, (thanks captain spudman and lieutenant Dinsdale, among others) so very low temperatures can't instantly be ruled out, but they will need further investigation.

The variation of barometer height (air pressure) with latitude is less well known, but just as interesting: this picture is dominated by the low pressure variability in the tropics (steady weather) and the much more variable pressure in the higher latitudes (anticyclones, depressions and storms). We can see very nicely the transition, in the southern hemisphere, from the steady trade-wind regions to the famous 'roaring forties' and 'furious fifties'.


Captains care about the air pressure because it warns them of changes in the wind. This sort of plot isn't ideal for showing winds, because the wind measurements are restricted to the Beaufort scale categories, but we can still see where the strong winds are to be found. Cruising in the North Atlantic, the Royal Navy's main stamping ground, was clearly no picnic: with temperatures down to freezing, variable weather and strong winds.


The Beaufort scale only goes up to 12; extensions are sometimes used for severe tropical storms, but the value of 15 recorded by HMS Cambrian in Rosyth dockyard in March 1919 is not credible. (Though I congratulate captain MamaLizard and the crew on correctly entering the value in the log - we always want the value written, even when it's obviously an error). If we disregard the Cambrian's exaggerations, there are four reports of wind force 12 so far, but they are all typographical errors - it's not much of a slip of the pen to turn '1-2' into '12'. We're still waiting for our first real hurricane.

dorbel

  • Ship history editors
  • Hero Member
  • *****
  • Posts: 502
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #1 on: February 03, 2011, 03:12:52 pm »
When you get "Foxglove" you will see a genuine 12 while in Japan, but I seem to think it was 10-12.

Janet Jaguar

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 7283
  • The sea is large; it knows more than any of us.
    • View Profile
    • Email
Re: Stanley to Archangel, and all points in between.
« Reply #2 on: February 03, 2011, 08:08:05 pm »
Philip, thank you.  These graphs are fascinating.  It's like I'm seeing global weather for real.

Something that cannot be distinguished from any composite graph but which has caught my attention more than once while transcribing:  Do the wind speeds flatten when a ship goes into dock, as opposed to just being in port someplace? 

I noticed it most when my ship was in dock at Chatham.  90% of the time (it felt like) there was nothing but Calm or Lt. Airs.  That quiet consistency has never happened on any ship of mine that is out on northern waters, so I just assumed that the Chatham docks provide very good shelter.

Just curious here. :)

philip.brohan

  • Old Weather Team
  • Full Member
  • *****
  • Posts: 164
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #3 on: February 03, 2011, 11:14:53 pm »
Janet.
 The wind speeds are definitely less in port than outside. I've not looked at the differences between ports (presumably some are more sheltered than others). Might well make an interesting study.
Philip


pliget

  • Full Member
  • ***
  • Posts: 121
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #4 on: February 04, 2011, 05:35:54 pm »
Most interesting as always and also useful in our transcribing.

I note Naneric where I spent some time today had force 11 winds in the mid-Atlantic en route to Halifax in March 1918. No 12s though.

Regarding the stray low temperatures off Canada maybe the Labrador current carried an iceberg or two to cause it? It would be interesting to see if it was an errant entry or something like that.


Caro

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3521
  • Our end is Life. Put out to sea. L. MacNeice
    • View Profile
« Last Edit: February 27, 2011, 08:07:24 am by Caro »

bpb42

  • Full Member
  • ***
  • Posts: 147
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #6 on: February 27, 2011, 01:04:49 pm »
Hi,
    can anyone tell what the date on that 'Laurentic' log page is, please ?

Many thanks,
                     Bernie

Tegwen

  • Ship history editors
  • Hero Member
  • *****
  • Posts: 1240
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #7 on: February 27, 2011, 01:44:55 pm »


I make it 12 October 1916, but it is not easy, so I would stand corrected if anyone who has spent time on her thinks different.

HTH
K

Caro

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3521
  • Our end is Life. Put out to sea. L. MacNeice
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #8 on: February 27, 2011, 02:02:10 pm »
Yes, it's 12 October 1916.  :)

bpb42

  • Full Member
  • ***
  • Posts: 147
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #9 on: February 27, 2011, 02:11:03 pm »
Thank you.
Regards,
              Bernie

cyzaki

  • Hero Member
  • *****
  • Posts: 855
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #10 on: February 27, 2011, 04:28:48 pm »
I thought I'd seen a hurricane somewhere!  ;D

Caro

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3521
  • Our end is Life. Put out to sea. L. MacNeice
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #11 on: June 02, 2011, 09:14:52 am »
There is a series of 12s here, from 9 pm onwards: http://oldweather.s3.amazonaws.com/ADM53-34119/ADM53-34119-017_1.jpg

Caro

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 3521
  • Our end is Life. Put out to sea. L. MacNeice
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #12 on: November 09, 2011, 08:19:07 pm »

bpb42

  • Full Member
  • ***
  • Posts: 147
    • View Profile

heffkit

  • Sr. Member
  • ****
  • Posts: 340
    • View Profile
Re: Stanley to Archangel, and all points in between.
« Reply #14 on: November 10, 2011, 04:10:15 am »
Thanks for this, Philip - it's really encouraging to see that this work is already beginning to be used, and showing interesting patterns.

Those plots are fascinating - are the results stable over time (i.e. if you do the same plots for each separate year, are they similar)?