Benjamin Franklin – Electrical Ambassador

(First published in new Zealand Geographic 96, March-April 2009)

We think of Benjamin Franklin as American, but for the first seventy odd years of his life he thought of himself as British. In turn, the British thought him one of theirs and embraced Franklin’s ideas and inventions as British discoveries.

For example, on his first voyage to New Zealand Captain Cook carried one of Franklin’s lightning conductors. Caught in a thunderstorm in Batavia (Jakarta), the Endeavour was struck by lightning but unharmed while a Dutch ship nearby had its mainmast shattered.

On 18 May 1773, during his second voyage to New Zealand, Cook was sailing the Resolution towards Stephen’s Island when he met with six waterspouts. As the sky darkened with cloud threatening strong winds, he ordered all sails “clewed up” to lessen the risk of damage. Four waterspouts rose and spent themselves between the ship and the land, a fifth was out to sea, but the sixth passed about 50 metres away from the stern of the Resolution.

Cook was familiar with Franklin’s theories about waterspouts, in particular, Franklin’s speculation that a large gun fired into one would disrupt it. Franklin, on horseback and armed with two pistols, had once chased a whirlwind down a country road in Virginia but it got away over a fence before he could shoot it. Cook endeavoured to try the experiment and ordered a cannon loaded and aimed but the waterspout had moved out of range by the time the gun was ready.

Franklin’s work on electricity won him international renown. The experiments he proposed, in a paper published by The Royal Society, proved that lightning was a form of electricity. This had long been the subject of speculation. Newton, for example, had described a spark jumping between the tip of a needle and a piece of amber rubbed with silk “The flame putteth me in mind of sheet lightning on a small – how very small – scale.”

Representation of waterspout accompanying "Water-spouts and Whirlwinds" by Benjamin Franklin. Figure III represents the semimagic square Benjamin Franklin constructed in 1750 having magic constant 260.

Franklin proposed building a sentry box on a tall tower with a 10 metre iron rod connected to an electrical stand. A person holding a grounded wire by insulated handles could draw sparks from the iron rod to the wire when an approaching thunderstorm charged the rod.

While Franklin waited for a tall tower to be built in Philadelphia he hit upon the idea of flying a kite into a storm and drawing sparks from a key attached to the kite string. By the time he successfully carried this out in June 1752 his original experiment had twice been successfully conducted in France, although news of this had not yet reached America.

Franklin was the first to use the terms positive and negative to describe electric charge. He also came up with the concepts of batteries and capacitors and the distinction between insulators and conductors.

Aside from explaining the nature of lightning, Franklin made other contributions to meteorology. He explained the paradox that an easterly storm could affect Philadelphia before it reached Boston, even though Boston lay further east. The answer was that the storm was a large whirling vortex of wind that moved eastwards across the land.

He correctly deduced from summertime hail that there must be a high layer in the atmosphere where temperatures were always as cold as winter. He astutely blamed volcanic eruptions in Iceland for “dry fog” experienced throughout the northern hemisphere in 1784 that brought an extremely cold winter.

Franklin had time to indulge in scientific speculations, as well as enter politics, because he had been so successful as a printer he was able to retire at forty-two. Among his popular productions was Poor Richard’s Almanack which contained information on tides, moon cycles, weather, sundry advice and pithy sayings such as “A countryman between two lawyers is like a fish between two cats.”

Borrowing a trick from Jonathon Swift, Franklin predicted the death of a rival. When the due date arrived, he pronounced the man dead. When his rival claimed to be still alive, Franklin dismissed the protests as a cruel hoax perpetrated by others trying to make money from the dead man’s name.

Franklin’s weather forecasts a year ahead were also tongue in cheek – “Ignorant men wonder how we astrologers fortell the weather so exactly…Alas! ‘tis easy as pissing abed. For instance: the stargazer peeps at the heavens through a long glass; he sees perhaps Taurus, or the great bull, in a mighty chase, stamping on the floor of his house, swinging his tail about …Distance being considered, and time allowed for all this to come down, there you have wind and thunder.”

Franklin’s scientific work made him the most famous American in Britain and Europe. He was the first person outside Britain to receive the Royal Society’s Coply medal. Hailed by the German philosopher Immanuel Kant as the “modern Prometheus”, Franklin was elected a foreign associate of the French Acadamy of Sciences and received honory degrees from numerous universities.

In politics he played a vital role in the decades before the American Revolution. Once war broke out, he helped write the Declaration of Independence then was given the crucial task of handling the French alliance. Hailed as the “electrical ambassador” in France, the French statesman Turgot said of Franklin “He snatched lightning from heaven and the sceptre from tyrants.” One portrait showed Franklin enthroned in the sky surrounded by winged deities with a lightning bolt behind him. Louis XVI, although helping the American cause, had a Sevres chamber pot made with Franklin’s portrait inside as a gift for one of Franklin’s admirers.

By the time Britain was defeated and a treaty negotiated, Franklin was eighty. Sailing home, he found time to measure the depth of the Gulf Stream using a corked bottle on a thirty-five fathom line. The pressure at depth forced the cork into the bottle followed by deep water. Pulled back to the surface, the water temperature was 12 F colder than the surface, proving that the Gulf Stream was a relatively shallow layer of warm water.

Back on land, Franklin returned to politics and helped revise the Constitution, before dying aged 83, one of the most remarkable statesmen-scientists the world has seen.

What’s causing the higher temps in Christchurch’s Eastern Suburbs?

Introduction

This short article is in response to an emailed complaint about temperatures displayed on the Christchurch Towns & Cities page on Thursday evening, 24 May 2012.

Sent: Thursday, 24 May 2012 10:26 p.m.
To: Enquiries
Subject: Christchurch weather issues!
 
Dear sir/madam,
I am writing regarding the situation with the Christchurch weather forecasts and current temperatures since the introduction of the split map into suburbs. I live in the eastern suburbs and have yet to see a day when the current temperature for the eastern suburbs has been correct! It is complete and utter rubbish and I am very intrigued to know where you are getting the temperatures from?
Attached is a screenshot image of your map this evening taken at 10.20pm …. I have just been outside and I can tell you for sure that the eastern suburbs are not currently at 12.7 degrees. More like around 6 degrees! Also I am certain that the port hills suburbs are not currently sitting at 17.9 degrees as I doubt anywhere in Canterbury reached that temperature today at all!
Chch sub-regional temps 10.20pm 24 May 2012
Please please get on top of this or at least put it back to just a temperature for Christchurch if you are unable to give us accurate readings and forecasts for the suburbs!
Many thanks

Situation

Situation at midnight 24 May 2012

This is the analysis chart for midnight 24/25 May 2012. It shows a strong northwest airstream across the South Island ahead of a cold front advancing from the southwest. It shows two troughs east of the South Island which were producing rain on the West Coast.

Fohn wind

This is a very good example of a “Fohn wind” situation. A Fohn wind is a hot and dry wind in the lee of a mountain range. The air is warmed by the latent heat given up by the condensing water vapour on the upwind side of the mountains. The condensed water falls there as rain and is no longer available to re-evaporate and potentially cool the air again as it descends on the lee side. Sometimes in Canterbury, this warm descending northwesterly wind flow is unable to displace the cool low-level northeasterlies which often precede a cold front. Higher locations like Sugar Loaf and Le Bons Bay are the first to show these higher temperatures as they protrude up into that wind flow.

There are certain geographical situations that will direct these warmer wind flows down to altitudes lower than would otherwise occur. One such location is the Port Hills – the wind flow “sticks” to the lee side and warmer temperatures (and strong northwesterlies) are experienced there.

Observations evening and overnight 24 May 2012

The “Eastern Suburbs” observations are taken from the New Brighton Pier automatic weather station. This graph is a plot of wind direction, wind speed and air temperature from that station between 8pm on 24 May and 8am 25 May 2012.

New Brighton Pier AWS data 8pm 24 May - 8am 25 May 2012

In the evening of the 24th the wind speed is fairly light, less than 10 km/h, and the direction is vary variable – sometimes from the west or northwest but mostly from the southeast. At 10:20pm the temperature was 12.6° and the wind was blowing from the southeast at 6.1 km/h. The “Port Hills” observations are taken from the Lyttelton Pier automatic weather station located at the Port. This graph is a plot of the same elements over the same period.

Lyttleton AWS data 8pm 24 May - 8am 25 May 2012

It shows a period between about 9pm and 1:30am when there was moderate to fresh northwesterlies. During that period the temperature had warmed from about 9° to 16-18° then lowering to 12-15° when the direction changed to northeast. This is clearly a Fohn wind.

The Fohn wind can also be seen in the data from Sugar Loaf:

Sugar Loaf data 3pm 24 May - noon 25 May 2012

With the strong northwesterlies, the temperature is 14-15° with low dew point and Relative Humidity – a typical Fohn wind. Note how the temperature fell dramatically as the wind direction changed to southerly.

The Fohn wind is also observed at Le Bons Bay:

Le Bons Bay data 3pm 24 May - noon 25 May 2012

At Christchurch Airport, the Fohn wind lowered to ground level only briefly, between 4am and 6am.

Christchurch Airport data noon 24 May - noon 25 May 2012

Note the difference in air temperature in relation to the wind direction. Later in the afternoon the direction was from northeast, off the sea. Later in the evening, the direction was more from the north and not from the sea; consequently the temperature was lower.

It appears to me that, apart from the Fohn wind flowing well above Christchurch (to be detected by the higher AWS sensors of Sugar Loaf and Le Bons Bay, and by Lyttelton in the down-slope wind there), there was a further complication, in that air from the northeast and east was warmer by a few degrees than air flowing from the north. I suspect that our email correspondent’s place is located in that northerly flow and it was that colder air stream that he experienced, rather than the warmer northeasterly airstream that was affecting the New Brighton Pier AWS.

Conclusion

Considering the larger meteorological situation on the evening of 24 May 2012, and the common behaviour of the Fohn wind (Canterbury Nor’wester) it seems to me that the weather stations around Christchurch were illustrating correctly the wind flows that were present and where their effects were being experienced.

New MetService Smartphone Apps

Yesterday saw the release of MetService’s new smartphone app, built for both iPhone and Android markets.

The app is location based, and includes the 10-day ‘Towns and Cities’ forecast, Severe Weather Warnings, latest video forecast from MetService TV, real-time rain radar and 3-day rain forecast, and traffic cams – all for your current location by default, and for all other NZ Towns & Cities via an easy-to-use menu.

There are some great interactive features, including the ability to share the forecast via Twitter and Facebook, and change out background images to personalise the app to your ‘weather mood’.  Interactive Manager Craig Delany says, “We love the idea of people being able to make the app their own by uploading a picture of their kids jumping in puddles for a rainy day forecast, or their favourite summer holiday snap for a sunny forecast”.

Find out more about these and other app features in the following video:

The MetService app is ad-free and available now for $2.59 on iTunes and Google Play.

Transit of Venus 6 June 2012

The Transit of Venus will take place on 6 June 2012, when the planet Venus crosses the face of the Sun.

This event has particular significance for New Zealanders, as in 1769 a Transit of Venus was the reason Captain James Cook first explored the Southern Pacific, and with the aid of the Tahitian navigator Tupaia travelled on to New Zealand.

The 2012 transit is perfectly timed for observers in New Zealand, as long as the weather is fine. You’ll need a clear view of the sun – but remember not to look directly at the sun without special viewing glasses. Your best chance to get a really good look is to attend one of the many public transit viewing events hosted by local astronomical societies and observatories around the country.

We’re providing special video forecasts for the Transit of Venus, so tune in to MetService TV to find out where the best viewing conditions will be around the country. And if the weather doesn’t cooperate, Carter Observatory will be live-streaming the event on site, as will the University of Canterbury on their website: http://www.phys.canterbury.ac.nz/venus_transit/

If you’re keen to learn more about the Transit and where to view it, here are some helpful websites to visit:

Stardome Observatory – Auckland: http://www.stardome.org.nz/

Carter Observatory – Wellington: http://www.carterobservatory.org/

Mt John Observatory – Lake Tekapo: http://earthandskynz.com

Radio New Zealand – excellent lectures: http://www.radionz.co.nz/national/lecturesandforums/transitofvenusarchives