Old New Zealand, HMS New Zealand, & new New Zealand

Atmospheric pressure along the route sailed by HMS New Zealand in 1919. The blue band shows the range of our estimates before oldWeather, the black points the new observations we provided, and the red band the revised analysis range incorporating our observations.

Atmospheric pressure along the route sailed by HMS New Zealand in 1919. The blue band shows the range of our estimates before oldWeather, the black points the new observations we provided, and the red band the revised analysis range incorporating our observations.

This week, atmospheric scientists are gathering in Queenstown, New Zealand, for the fifth general assembly of the SPARC program (Stratosphere-troposphere Processes And their Role in Climate). We’ve mentioned New Zealand before: both as a country who’s isolation means that its historical weather is poorly documented, and as a Battlecruiser in the original oldWeather fleet. In September 1919 the two met: the battlecruiser visited the country, giving us an opportunity to make a major improvement in reconstructing the climate of the region.

As we showed back in October, we’re now re-doing our analysis of global weather, so we can see exactly how much the observations we’ve recovered from HMS New Zealand have improved our knowledge of the climate of New Zealand (the country). The figure above (made for the SPARC meeting) shows our estimates of the weather in each region visited by HMS New Zealand during her circumnavigation in 1919: blue for before oldWeather, and red a new revision using our observations. The width of the band indicates uncertainty – narrower is better – and the improvement we’ve made is very large.

6 responses to “Old New Zealand, HMS New Zealand, & new New Zealand”

  1. Craig Gaston says :

    These graphs appear to be for specific dates, as I would expect given the data source. So my question is, Philip, what inferences can you make for other dates in these regions for which we don’t have any observations? I am wondering how useful it is if we only have a couple of voyages in “grey” regions?

    Thanks.

    • Philip says :

      To narrow our uncertainty, we need local observations. Any time and place where there are no observations close in space or time will have a large uncertainty, but each observation can spread improvement over a wide region. One of the virtues of the reanalysis is that we have uncertainty information for every time and date – of course, it’s hard to display, or even analyse, that much information. The best illustration I’ve managed so far is shown in https://blog.oldweather.org/2013/10/12/brightening-the-world/ : the yellow areas are the regions where the reconstruction is notably improved.

      The equivalent for 1919 is shown at https://vimeo.com/81375606. If you watch that in August & September you will see HMS New Zealand cross the Tasman Sea, and you can judge for yourself the size and duration of the cloud of information she carries.

      • Craig says :

        For “yellow areas” I presume you are referring to the yellow caterpillar-like objects that move across the map (because they persist even after the ship has passed a point, and not the yellowish-brown clouds that sometime surround them because if it’s the latter, they sometimes occur even when there are no “caterpillars” nearby?

        Regarding the narrowing of uncertainty, I can understand if an observation falls outside the uncertainty range for a time and space where the ship has passed that this would be useful information, but I don’t understand how one point is space and time within the range could spread improvement over a wider region. It does support the hypothesis that the estimated range is valid but how can it narrow that range?

      • Yvan Dutil says :

        Craig, it is the clouds. Improvement occurs both due to new data and improvement in the model. Also, atmospheric perturbations propagate. Hence, the new data improve a much large surface area than what you might expect.

Trackbacks / Pingbacks

  1. Uncertainty uncertainty | Old Weather Blog - September 11, 2014
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