The thing about wind

I’ve written before about my frustration/hatred of wind in daily life, but today I wanted to raise another complaint: using wind data in past climate research.

Wind direction is easy and cheap to monitor. All you really need is a damp finger and a decent sense of which way is north.

The strength of wind has also been observed for a long time, for its vital role in turning windmills and pushing ships.

But the thing about local wind information, is that it’s just not great for climate research.

The ease of watching the wind does not make up for that fact that it’s a pain in the arse to analyse when you are looking at long term changes in the climate.

And wind is predicted to change. A warmer earth means stronger weather systems and a shift in global wind patterns. This will in turn affect ocean currents and sea ice coverage and lots of other important things. So, we need to know how the wind is changing.

But historical wind records can be more like a drama queen than a reliable source of climate information:  irrational and highly sensitive to the smallest changes.

Wind data can be subjective

Wind observations have been taken for centuries, long before technical weather instruments like anemometers were used. Observing wind strength and direction was a vital part of any sailors’ duties, at land and sea. While direction could be recorded relatively accurately using a compass, converting what you see around you to a number is a subjective thing.

Here, for example, is the famous Beaufort scale (discussed in loving detail in this book):

Beaufort
The Beaufort scale for both land and sea, along with the associated estimated wind speed. Source: Howtoons

Now these descriptions are poetic, but what if you aren’t near a chimney, or any small branches?

Or, what if your wind strength scale had slightly different descriptions?

Francis Beaufort was not the only guy trying to turn the chaotic experience of wind into a numerical scale. During my recent work with historical wind data in Europe, I came across the Beaufort scale, a French wind strength scale and a nine-point strength scale used in Turkey. These indices all use different definitions to approximate the strength of wind.

Even worse, today, we use the speed of the wind to study it, so these values need to be converted to something approximating metres per second, or kilometres per hour, or knots, or cyclone scales, or tornado strengths.

Do you see where I’m going with this? Combining all of these different methods of measuring how strong and/or fast the wind is it a tricky job. It also means that we are comparing data with say, 13 different levels (0–12 on the Beaufort scale), with data that have many more (an anemometer can measure at 0.05 m/s intervals).

This is almost, but not quite, an apples and oranges scenario.

Also, wind data are mighty sensitive

Even once the Beaufort scale was replaced with good ole’ technology, wind data can still easily be rubbish, because they are extremely sensitive to the local environment.

This is fine if you are recording the wind at an airport for safe landings, or to see if a wind tunnel has accidentally been made, but if you want to look at large wind patterns over a long period of time, you might be in trouble.

The growth of a tree nearby, the erection (teehee) of a building across the road, or a small change in the location or height of the instrument can have a big impact on wind data. Temperature, rainfall and other weather variables can also be affected by these things, but wind observations are particularly fussy.

badwindexample
An example of wind speed being affected by local changes. Image: World Meteorological Organisation, so you know it’s legit.

It’s not all bad

I realise it sounds a lot like I’m saying observing wind is a waste of time. But things aren’t quite that bleak.

Understanding local wind is really important for many things, like renewable energy, aviation safety and urban planning.

And, to be fair, wind observations taken at sea are generally much better than on the land, due to the lack of trees, buildings and other terrestrial nonsense.

Climate models are also pretty good at deriving large-scale winds from air pressure observations, so most long-term wind studies looking at climate change use models instead.

Finally, there are methods of correcting the non-climate features in wind data, if you are careful and have good information about the weather stations (it’s been done in Canada for example, and the Iberian Pensinsula).

But be careful next time you explore some old wind data. There’s a hidden drama queen in there, who might be telling you more about the neighbour’s pine trees than climate change.

How’s about that weather then? 26 and 28 March 1844

People love talking about the weather. Whether it’s on Twitter in 2017, or in letters to the Editor in 1841, we are never short of a meteorological-based conversation starter, particularly in Australia.

The aim of these posts is to share some of the events that piqued people’s interest back in the day. Not always the hottest, driest, coldest or wettest day, but some days that got people whinging.

During this week in 1844, Sydney experienced a swing of temperatures which was echoed across the colony of New South Wales.

The Morning Chronicle reported a 6am temperature of 43ºF (6.1ºC) on the morning of 26 March 1844. This was the coldest March morning in the 10 years of published observations in the paper, although there is no information about where the thermometer was kept, so the data may not be that accurate.

26_March_temp
Morning Chronicle, 27 March 1844.

Chilly mornings and premature frosts were also reported in the Hunter Valley, where correspondents claimed that the nights were “unusually cold for the season of the year”.

Two day later, on Thursday 28 March 1844, hot north winds with associated dust came upon Sydney in a late summer blast. George Peacock, the trained observer at South Head, on Sydney’s coast, wrote:

At about two o’clock am came on to blow very hard from north and north-westward, and subsequently, during the morning, moderated: atmosphere bright and clear. Just at noon a violent squall of hot wind came over from north-west by north, carrying along with it clouds of dust—and continued a hot and very strong wind till near sunset — veering towards west-north-west; atmosphere being very thick and hazy, but cloudless.

The highest temperature Peacock recorded that day was 87 ºF (30 ºC) at 2:30 p.m., up from 74ºF (23.3 ºC) at 8:30 that morning. The Chronicle reported a noon temperature of 80ºF, but interestingly a southeasterly wind, again suggesting that the observations weren’t done under the most rigorous conditions (read: maybe the paperboy took them??)

Regional correspondents also reported the hot blustery day. In Goulburn, southern NSW, the wind on the 29th was “unusually violent. Indeed the most disagreeable day we have had for a long season. Rain is much wanted to put the land in condition for the plough”. James Waugh at Jamberoo, also in southern New South Wales, recorded a maximum temperature of 90 ºF (32.2 ºC) in his diary (available at the State Library of New South Wales), with hot and windy weather.

The Hunter Valley felt the effects of the hot northerly too. On the 2nd of April, a Morpeth resident “of upwards of forty years” wrote to the Sydney Morning Herald of their fears that their sunflowers would “be apt to blights from the hot winds – that have been the case (in a great measure) this season”.

On the 6th, the word from Muswellbrook in the upper Hunter was that “The weather has recently been very sultry, and the late corn has suffered severely from hot winds”.

Hot winds like those experienced on 28 March are a common feature of Sydney’s climate. HC Russell, NSW’s Government Astronomer from 1870–1903, was interested in Sydney’s hot winds, dedicating several pages to the subject in his extensive 1877 summary of the climate of NSW. He wrote:

Of all the features of the climate of Australia the hot wind is in many respects one of the most remarkable and interesting, as it is the key which opens the explanation of the whole of our wind system….In character this wind is the most disagreeable known in Australia.

Tangent!

While the term wasn’t used at the time, the 28th of March sounds like a classic “brickfielder”, a strong dusty wind that blows during the summer months.

The term “brickfielder” was bandied about in the mid to late 1800s across southern Australia. According to this neat article, a brickfielder in the southern states was a hot dusty northerly, while in New South Wales it originally referred to a cool southerly wind which blew red dust from the brickworks into Sydney town.

Brickfielder
Sydney Gazette and New South Wales Advertiser, 10 March 1836.

It might be that in Sydney, a “brickfielder” was any old wind that brought dust with it. On 10 March 1836 for example, The Sydney Gazette and New South Wales Advertiser reported that a brickfielder had occurred “Tuesday last”.

The weather observations for that Tuesday last show a strong north north west wind, with high temperatures too.

brickfielder_data
Sydney Gazette and New South Wales Advertiser, 10 March 1836. 

In 2010, the Australian Meteorological and Oceanography Society ran a competition to give Melbourne’s dusty winds their own name, with the winner being the “Northerly Duster”. Is it yet to catch on.

Teleco-what now?

This post contains a lot of links to scientific articles that may be paywalled, or just as bad, really technical. Just let me know if you need a copy of any of them, or if they don’t make sense.

Ah, teleconnection. What a word. Much like ‘madrugada‘ does not have a translation into English, or ’serendipity‘ does not have a Spanish equivalent, teleconnection is a term that is hard to translate into normal words without it losing some of its beauty.

But let me have a try. Essentially, teleconnections are the connections between weather and climate in one place, and weather and climate in another. No, that’s not it. A teleconnection is the remote influence of large-scale atmospheric circulation patterns. No that’s worse. It’s the effect that the climate in one place can have somewhere else. It’s teleconnection.Read More »