How do newly rescued pressure observations help reconstruct the weather?

The pressure observations that are being rescued will have a large demonstrable effect on our knowledge of past weather.

In the graphic below, the left hand side always shows our current estimates of the locations of the isobars (lines of equal pressure) for 9am on 26th February 1903. There are 80 different sets of lines, each of which are considered equally likely given the information currently available. There is not much agreement over western Europe, so it looks very messy!

The animation on the right hand side shows how confident we become when individual observations (red dots) are added one by one. Starting in southern Europe the isobars gradually begin to become better defined until a much clearer picture emerges when all 55 newly rescued observations have been added.

We will be repeating this process for the whole 1900-1910 period that we are rescuing data for so that we can see the improvements in detail. This will demonstrate the value of this data for answering interesting science questions about how the circulation of the atmosphere varies over time.

An analogy is that we currently have blurred ‘polaroid’ pictures of the weather at this time, but gradually we are sharpening the image. As we add observations the picture becomes more like a digital photo.

[Very technical details: this animation uses all 80 members from v3 of the 20th Century Reanalysis and an offline version of the Ensemble Kalman Filter to assimilate the new observations.]

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1 million observations!

1644 volunteers have now helped rescue over 1 million daily weather observations from 61 locations all over Europe during 1900-1906! Thank you!

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Grey regions indicate where there is missing or uncertain data. Often this will be due to a station joining or leaving the Daily Weather Report logs. Some of these gaps will be filled in during the quality control phase of the project.

Examining the rescued pressure data

The Weather Rescue volunteers have now rescued all the observations written in the Daily Weather Reports for 1900-1903, so it’s time to have a closer look at some of the data. We’ve picked October 1903 as this is the wettest month ever recorded in the UK.

The video below, made by Philip Brohan, looks complicated at first. The left hand side shows an animation of our previous understanding of the atmospheric pressure, for every hour during October 1903. This is produced using a modern weather forecasting model, but the simulations do not include the information in the new rescued observations, which are shown as the red dots.

There are several blue lines on the map (looking a bit like spaghetti!) which show the pressure in different simulations of the past. Because we don’t currently have that many observations to constrain the weather patterns there is a lot of uncertainty about where some of the pressure features are. The thicker black lines show the pressure contours where we are more confident.

The right hand side lists the weather stations in the Daily Weather Reports, and the red bars show the rescued pressure observations. The blue dots show the different simulations for that location and time.

There are lots of interesting features to note. You may notice that the maps often have a sharp adjustment – these are the times at which the existing data is ‘assimilated’ into the simulations. Often the blue dots in the right hand panel show a wide range – when the new observations are included then this uncertainty will reduce substantially. Sometimes the existing simulations (blue dots) are close to the new observations (red bars), but often not. It is these occasions where the new data has most value, and we expect the blue ‘spaghetti’ lines to become much closer to each other.

Importantly, the improvements will be largest when low pressure storms are passing near the stations. We want to learn about the frequency of intense storms in the past to compare with now and these rescued observations will significantly improve our understanding.

We have also made an animation of the rainfall data rescued so far in 1903. Note October in particular as being a very wet month for the UK!

Queen Victoria and the Herøy ‘hurricane’

On the evening of 22nd January 1901 Queen Victoria died after reigning over the UK since 1837. On the same day, a ‘hurricane’ killed 35 people in Herøy in north-western Norway. What can we understand about the weather that long ago?

We now have the ability to reconstruct the weather on any particular day as far back as 1900 (at least) by combining our modern weather forecast models with the available measurements from the day in question. But, the further back in time we look, the more uncertain we are, as the available observations become fewer. Continue reading

Phase 1 complete!

After just 10 weeks, the 3656 Operation Weather Rescue volunteers have completed the transcription of all the hourly rainfall, temperature and pressure data taken on Ben Nevis and in Fort William between 1883 and 1904!

There was skepticism from many about whether this citizen science approach to rescuing historical weather data would work.

It has. And, it has far exceeded our expectations.

The amazing volunteers have given their time and made a real difference to our understanding of past weather and climate. Thank you. Continue reading

41311 days

41311 days have elapsed since the Ben Nevis weather observatory shut at the end of September 1904.

And now there is a weather station at the summit again!

BBC article: http://www.bbc.co.uk/news/science-environment-41918646

Listen to BBC radio piece: http://www.bbc.co.uk/programmes/p05mhqj5

Short video and photos taken by mountain guide Ron Walker of the weather station installation

Lots more pictures & longer video, including the ruins of the old observatory: https://drive.google.com/drive/folders/1RshYT9bgUxHAbv7uS-nB4cKGh2tbgOJF

STV article: https://stv.tv/news/north/1401809-station-on-ben-nevis-records-weather-for-first-time-since-1904/

February 1903 – the Ulysses storm

In late February 1903, a large storm came across Ireland and Scotland. It is believed to have inspired a small passage in the novel Ulysses by James Joyce:

O yes, J.J. O’Molloy said eagerly. Lady Dudley was walking home through the park to see all the trees that were blown down by that cyclone last year and thought she’d buy a view of Dublin.

The storm caused structural damage to many regions, and uprooted trees.
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Our current best view of the storm comes from the 20th Century Reanalysis – this is essentially a modern weather forecast model used to simulate past weather by filling in the gaps between the fairly limited observations available. Continue reading

Using the rescued weather data

Once we’ve rescued all the weather observations, what are we going to do with them?

The first step will be to publish the data as an academic paper. We will choose an open access journal such as Earth System Science Data or Scientific Data. As well as the pressure, temperatures, rainfall and wind observations, we will also produce estimates of the humidity, derived from the pressure and temperature observations.

We would welcome suggestions on how we might best acknowledge the contributions of all our volunteers in this publication.

Once the data is published we will send copies to the various international weather data archives such as ISPD (pressure), GHCN (rainfall, temperature), ISTI (temperature) and a new European initiative which is collecting all meteorological data. The UK Met Office will also put the data into its MIDAS data archive.

This will ensure the data is available as widely as possible for anyone to analyse and use. For example, the data will be incorporated into the next generation of UK climate observations (called UKCP18), the Berkeley Earth global temperature datasets, and the Twentieth Century Reanalysis.

These are important steps to ensure the data can be used in the bigger picture of understanding how the UK and global climate has changed. Similar ‘data rescue’ activities are happening all over the world and continually adding to our knowledge of past weather. We firmly believe that better understanding of how the weather has already changed can better inform how it might change further in future.

With the funding that we have available we will focus on how extreme weather in western Scotland has changed between the time the observations were taken and now, particularly heavy rainfall. We will also use the data to better understand mountain meteorology, and especially atmospheric inversions (when the summits are warmer than lower levels).

In a separate project we are also trawling the detailed notes that accompany the weather observations to learn about the aurorae that were visible from the summit. Our space weather partners will be using these observations to better understand variations in the sun’s output.

But, there are also likely to be unexpected findings that we cannot anticipate. If anyone has any suggestions for analysis, we would love to discuss these. This is your project too!

And, if you’re anywhere near Edinburgh from 17th-19th November, come along to the free NERC UnEarthed showcase at Dynamic Earth, where we will have an exhibit.

Cloudy inspiration

Although we are focussed on rescuing the weather data taken by the meteorologists, the observatory at the summit of Ben Nevis is also famous for providing the inspiration for C.T.R. Wilson to invent the cloud chamber.

This invention, for which he won the Nobel Prize in 1927, was used to track particles as they passed through super-saturated air. The cloud chamber was later used to make other Nobel Prize winning discoveries of new fundamental particles such as the positron. Continue reading

Weathermen of Ben Nevis

For twenty years between 1883 and 1904, three intrepid meteorologists lived at the top of Ben Nevis – the highest mountain in the UK – experiencing some of the worst weather the country has to offer.

Every hour, day and night, winter and summer, and whatever the weather, one of them would step outside and check the meteorological instruments, diligently recording the observations.

This was a uniquely Victorian-era endeavour. Science for the sake of science. Rather than exploring the world’s polar regions like some of their contemporaries, these Weathermen of Ben Nevis were exploring the atmosphere.

There was simply no other way of learning in detail about how the atmosphere changed with height without living at the top of a mountain. So that is what they did.

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Continue reading