Posts Tagged ‘Weather’

Ignorance: Eggs & Weather Forecasts

November 26, 2018

Every so I often I learn something so simple and shocking that I find myself asking:

How can I possibly not have known that already?“.

Eggs

Eggs

Eggs

While listening to Farming Today the other morning, learned that:

Large eggs come from old hens

In order to produce large eggs – the most popular size with consumers – farmers need to allow hens to reach three years old.

So during the first and second years of their lives they will first lay small eggs, then medium eggs, and finally large eggs.

On Farming Today a farmer was explaining that egg production naturally resulted a range of egg sizes, and it was a challenge to find a market for small eggs. Then came the second bomb’shell’.

The yolk is roughly same size in all eggs

What varies between small and large eggs is mainly the amount of egg white (albumen).

How could I have reached the age of 58 and not  known that? Or not have even been curious about it?

Since learning this I have become a fan of small eggs: more yolk, less calories, more taste!

But my deep ignorance extends beyond everyday life and into the professional realm. And even my status as ‘an expert’ cannot help me.

Weather Forecasts & Weather Stations

Professionally I have become interested in weather stations and their role in both Numerical Weather Prediction (NWP, or just weather forecasting) and in Climate Studies.

And as I went about my work I had imagined that data from weather stations were used as inputs to NWP algorithms that forecast the weather.

But in September I attended CIMO TECO-2018 (Technical Conference on Meteorological and Environmental Instruments and Methods of Observation) in Amsterdam.

And there I learned in passing from an actual expert, that I had completely misunderstood their role.

Weather station data is not considered in the best weather forecasts.

And, on a moment’s reflection, it was completely obvious why.

Weather forecasting work like this:

  • First one gathers as much data as possible about the state of the atmosphere ‘now’. The key inputs to this are atmospheric ‘soundings’:
    • Balloon-borne ‘sondes’ fly upwards through the atmosphere sending back data on temperature, humidity and wind (speed and direction) versus height.
    • Satellites using infrared and microwave sensors probe downwards to work out the temperature and humidity at all points in the atmosphere in a swathe below the satellite’s orbit.
  • The NWP algorithms accept this vast amount of data about the state of the atmosphere, and then use basic physics to predict how the state of the entire atmosphere will evolve over the coming hours and days

And then, after working out the state of the entire atmosphere, the expected weather at ground level is extracted.

Visualisation of the amount of moisture distributed across different heights in the atmosphere based on a single pass of a 'microwave sounding' satellite. Image credit: NASA/JPL-Caltech

Visualisation of the amount of moisture distributed across different heights in the atmosphere based on a single pass of a ‘microwave sounding’ satellite. The data gathered at ground level is just a tiny fraction of the data input to NWP models. Image credit: NASA/JPL-Caltech

Ground-based weather stations are still important:

  • They are used to check the outputs of the NWP algorithms.
  • But they are not used as inputs to the NWP algorithms.

So why did I not realise this ‘obvious’ fact earlier? I think it was because amongst the meteorologists and climate scientists with whom I spoke, it was so obvious as to not require any explanation.

Life goes on

So I have reached the age of 58 without knowing about hen’s eggs and the role of weather stations in weather forecasting?

I don’t know how it happened. But it did. And I suspect that many people have similar areas of ignorance, even regarding aspects of life with which we are totally familiar – such as eggs – or where one is nominally an expert.

And so life goes on. Anyway…

This pleasing Met Office video shows the importance of understanding the three-dimensional state of the atmosphere…

And here is a video of some hens

 

How hard did it rain last week?

August 22, 2014

Hardcore Protonistas – and that’s you if you are reading this – will know that I love measuring things.

I love the way that measurements allow an extra level of wonder at the intricate detail of the world around us.

The rate of rainfall at NPL Teddington on 14th August 2014. The rainfall rate initially exceed 100 mm per hour. The first event resulted in 28 mm of rain and the second 18 mm of rain.

The rate of rainfall at NPL Teddington on 14th August 2014. The rainfall rate initially exceed 100 mm per hour. The first event resulted in 29.3 mm of rain and the second 18.4 mm of rain.

Last Thursday 14 August 2014 there were two torrential rain events at NPL.

They were kind of event that makes you stop what you are doing, go to the window and just stare. Personally they evoked memories of my childhood home and the security of being indoors and protected.

All very nice. But how much rain fell? And was it exceptional? These questions can only be answered by looking at data.

So I downloaded data from a weather station on the roof of one of NPL’s buildings. The graph at the top of the page shows the key features of the data.

  • In both events the rate of rainfall was initially over 100 millimetres per hour
  • The first event deposited 29.3 mm of rain and the second 18.4 mm of rain.

These data show that these were indeed powerful weather events.

Over the main NPL site, which comprises approximately 400 m  x 100 m = 40,000 square metres, the first event result in the deposition of approximately 1160 tonnes of water in approximately 50 minutes. Wow!

But were the events exceptional? The Met Office keep a record of extreme weather events (Link) which states that the most extreme UK rainfall events have been:

  • Highest 5-minute total: 32 mm on 10 August 1893 Preston (Lancashire)
  • Highest 30-minute total: 80 mm on 26 June 1953 Eskdalemuir (Dumfries & Galloway)
  • Highest 60-minute total: 92 mm on 12 July 1901 Maidenhead (Berkshire)

Assuming these historic measurements are indeed reliable – which is not always the case – then the events in Teddington last week  were not technically ‘extreme’.

However they were astounding – and in the very best sense of the word – wonder-ful.


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